PCM not letting heat/AC blower blow?
07-19-2006, 05:35 PM
#11
Guest
Posts: n/a
Re: PCM not letting heat/AC blower blow?
billy ray wrote:
> Perhaps someone on the board has a ZJ manual.
That would be fantastic.
> It is my somewhat fuzzy
> understanding that the slower speeds are controlled through a trouble prone
> multi-resister block and the high speed goes straight through the switch.
It is, but the resister block seems to be working fine:
>> If I hook the far side of the relay to ground, the blower blows.
and I can control the speed with the switch.
>
>
> "Carl K" <carl@personnelware.com> wrote in message
> news:pOydnfaDzraa6iPZnZ2dnUVZ_radnZ2d@comcast.com. ..
>> Pretty sure this is how my 97 Grand Cherokee is wired: (I may make it to
>> the library to confirm - Haynes wiring didn't have it.)
>>
>> Battery(+) -- 40A fuse -- motor -- resistor pack == switch -- relay --
>> Powertrain Control Module -- Battery(-)
>>
>> the == is 4 wires, 1 for each speed
>>
>> If I hook the far side of the relay to ground, the blower blows. The
>> relay is controlled by both ignition and vent selector, so just making a
>> permanent connection to ground would leave me with a fully functional
>> system.
>>
>> But before I go with that hack, wondering if I am missing something?
>>
>> The PCM is $480+installation required to program it.
>>
>> Will a "diagnostic code reader" ($99 from local auto store) tell me if the
>> PCM is not letting the blower blow?
>>
>> Also, $99 gets me "just numeric codes for '96 and up" but $250 get a
>> 'delux' that works on "all cars" and gives descriptions. the 97 is the
>> only car I have that has any sort of diag system (like it will do my 68
>> pickup any good) - and I somehow doubt the delux will really tell me
>> everything I need to know anyway. any comments?
>>
>>
>> Carl K
>
>
> Perhaps someone on the board has a ZJ manual.
That would be fantastic.
> It is my somewhat fuzzy
> understanding that the slower speeds are controlled through a trouble prone
> multi-resister block and the high speed goes straight through the switch.
It is, but the resister block seems to be working fine:
>> If I hook the far side of the relay to ground, the blower blows.
and I can control the speed with the switch.
>
>
> "Carl K" <carl@personnelware.com> wrote in message
> news:pOydnfaDzraa6iPZnZ2dnUVZ_radnZ2d@comcast.com. ..
>> Pretty sure this is how my 97 Grand Cherokee is wired: (I may make it to
>> the library to confirm - Haynes wiring didn't have it.)
>>
>> Battery(+) -- 40A fuse -- motor -- resistor pack == switch -- relay --
>> Powertrain Control Module -- Battery(-)
>>
>> the == is 4 wires, 1 for each speed
>>
>> If I hook the far side of the relay to ground, the blower blows. The
>> relay is controlled by both ignition and vent selector, so just making a
>> permanent connection to ground would leave me with a fully functional
>> system.
>>
>> But before I go with that hack, wondering if I am missing something?
>>
>> The PCM is $480+installation required to program it.
>>
>> Will a "diagnostic code reader" ($99 from local auto store) tell me if the
>> PCM is not letting the blower blow?
>>
>> Also, $99 gets me "just numeric codes for '96 and up" but $250 get a
>> 'delux' that works on "all cars" and gives descriptions. the 97 is the
>> only car I have that has any sort of diag system (like it will do my 68
>> pickup any good) - and I somehow doubt the delux will really tell me
>> everything I need to know anyway. any comments?
>>
>>
>> Carl K
>
>
07-19-2006, 05:35 PM
#12
Guest
Posts: n/a
Re: PCM not letting heat/AC blower blow?
billy ray wrote:
> Perhaps someone on the board has a ZJ manual.
That would be fantastic.
> It is my somewhat fuzzy
> understanding that the slower speeds are controlled through a trouble prone
> multi-resister block and the high speed goes straight through the switch.
It is, but the resister block seems to be working fine:
>> If I hook the far side of the relay to ground, the blower blows.
and I can control the speed with the switch.
>
>
> "Carl K" <carl@personnelware.com> wrote in message
> news:pOydnfaDzraa6iPZnZ2dnUVZ_radnZ2d@comcast.com. ..
>> Pretty sure this is how my 97 Grand Cherokee is wired: (I may make it to
>> the library to confirm - Haynes wiring didn't have it.)
>>
>> Battery(+) -- 40A fuse -- motor -- resistor pack == switch -- relay --
>> Powertrain Control Module -- Battery(-)
>>
>> the == is 4 wires, 1 for each speed
>>
>> If I hook the far side of the relay to ground, the blower blows. The
>> relay is controlled by both ignition and vent selector, so just making a
>> permanent connection to ground would leave me with a fully functional
>> system.
>>
>> But before I go with that hack, wondering if I am missing something?
>>
>> The PCM is $480+installation required to program it.
>>
>> Will a "diagnostic code reader" ($99 from local auto store) tell me if the
>> PCM is not letting the blower blow?
>>
>> Also, $99 gets me "just numeric codes for '96 and up" but $250 get a
>> 'delux' that works on "all cars" and gives descriptions. the 97 is the
>> only car I have that has any sort of diag system (like it will do my 68
>> pickup any good) - and I somehow doubt the delux will really tell me
>> everything I need to know anyway. any comments?
>>
>>
>> Carl K
>
>
> Perhaps someone on the board has a ZJ manual.
That would be fantastic.
> It is my somewhat fuzzy
> understanding that the slower speeds are controlled through a trouble prone
> multi-resister block and the high speed goes straight through the switch.
It is, but the resister block seems to be working fine:
>> If I hook the far side of the relay to ground, the blower blows.
and I can control the speed with the switch.
>
>
> "Carl K" <carl@personnelware.com> wrote in message
> news:pOydnfaDzraa6iPZnZ2dnUVZ_radnZ2d@comcast.com. ..
>> Pretty sure this is how my 97 Grand Cherokee is wired: (I may make it to
>> the library to confirm - Haynes wiring didn't have it.)
>>
>> Battery(+) -- 40A fuse -- motor -- resistor pack == switch -- relay --
>> Powertrain Control Module -- Battery(-)
>>
>> the == is 4 wires, 1 for each speed
>>
>> If I hook the far side of the relay to ground, the blower blows. The
>> relay is controlled by both ignition and vent selector, so just making a
>> permanent connection to ground would leave me with a fully functional
>> system.
>>
>> But before I go with that hack, wondering if I am missing something?
>>
>> The PCM is $480+installation required to program it.
>>
>> Will a "diagnostic code reader" ($99 from local auto store) tell me if the
>> PCM is not letting the blower blow?
>>
>> Also, $99 gets me "just numeric codes for '96 and up" but $250 get a
>> 'delux' that works on "all cars" and gives descriptions. the 97 is the
>> only car I have that has any sort of diag system (like it will do my 68
>> pickup any good) - and I somehow doubt the delux will really tell me
>> everything I need to know anyway. any comments?
>>
>>
>> Carl K
>
>
07-19-2006, 05:35 PM
#13
Guest
Posts: n/a
Re: PCM not letting heat/AC blower blow?
billy ray wrote:
> Perhaps someone on the board has a ZJ manual.
That would be fantastic.
> It is my somewhat fuzzy
> understanding that the slower speeds are controlled through a trouble prone
> multi-resister block and the high speed goes straight through the switch.
It is, but the resister block seems to be working fine:
>> If I hook the far side of the relay to ground, the blower blows.
and I can control the speed with the switch.
>
>
> "Carl K" <carl@personnelware.com> wrote in message
> news:pOydnfaDzraa6iPZnZ2dnUVZ_radnZ2d@comcast.com. ..
>> Pretty sure this is how my 97 Grand Cherokee is wired: (I may make it to
>> the library to confirm - Haynes wiring didn't have it.)
>>
>> Battery(+) -- 40A fuse -- motor -- resistor pack == switch -- relay --
>> Powertrain Control Module -- Battery(-)
>>
>> the == is 4 wires, 1 for each speed
>>
>> If I hook the far side of the relay to ground, the blower blows. The
>> relay is controlled by both ignition and vent selector, so just making a
>> permanent connection to ground would leave me with a fully functional
>> system.
>>
>> But before I go with that hack, wondering if I am missing something?
>>
>> The PCM is $480+installation required to program it.
>>
>> Will a "diagnostic code reader" ($99 from local auto store) tell me if the
>> PCM is not letting the blower blow?
>>
>> Also, $99 gets me "just numeric codes for '96 and up" but $250 get a
>> 'delux' that works on "all cars" and gives descriptions. the 97 is the
>> only car I have that has any sort of diag system (like it will do my 68
>> pickup any good) - and I somehow doubt the delux will really tell me
>> everything I need to know anyway. any comments?
>>
>>
>> Carl K
>
>
> Perhaps someone on the board has a ZJ manual.
That would be fantastic.
> It is my somewhat fuzzy
> understanding that the slower speeds are controlled through a trouble prone
> multi-resister block and the high speed goes straight through the switch.
It is, but the resister block seems to be working fine:
>> If I hook the far side of the relay to ground, the blower blows.
and I can control the speed with the switch.
>
>
> "Carl K" <carl@personnelware.com> wrote in message
> news:pOydnfaDzraa6iPZnZ2dnUVZ_radnZ2d@comcast.com. ..
>> Pretty sure this is how my 97 Grand Cherokee is wired: (I may make it to
>> the library to confirm - Haynes wiring didn't have it.)
>>
>> Battery(+) -- 40A fuse -- motor -- resistor pack == switch -- relay --
>> Powertrain Control Module -- Battery(-)
>>
>> the == is 4 wires, 1 for each speed
>>
>> If I hook the far side of the relay to ground, the blower blows. The
>> relay is controlled by both ignition and vent selector, so just making a
>> permanent connection to ground would leave me with a fully functional
>> system.
>>
>> But before I go with that hack, wondering if I am missing something?
>>
>> The PCM is $480+installation required to program it.
>>
>> Will a "diagnostic code reader" ($99 from local auto store) tell me if the
>> PCM is not letting the blower blow?
>>
>> Also, $99 gets me "just numeric codes for '96 and up" but $250 get a
>> 'delux' that works on "all cars" and gives descriptions. the 97 is the
>> only car I have that has any sort of diag system (like it will do my 68
>> pickup any good) - and I somehow doubt the delux will really tell me
>> everything I need to know anyway. any comments?
>>
>>
>> Carl K
>
>
07-19-2006, 07:45 PM
#14
Guest
Posts: n/a
Re: PCM not letting heat/AC blower blow?
"Carl K" <carl@personnelware.com> wrote in message
news:Ad-dnScCL541OCPZnZ2dnUVZ_qWdnZ2d@comcast.com...
> Mike wrote:
>> "Carl K" <carl@personnelware.com> wrote in message
>> news:pOydnfaDzraa6iPZnZ2dnUVZ_radnZ2d@comcast.com. ..
>>> Pretty sure this is how my 97 Grand Cherokee is wired: (I may make it to
>>> the library to confirm - Haynes wiring didn't have it.)
>>>
>>> Battery(+) -- 40A fuse -- motor -- resistor pack == switch -- relay --
>>> Powertrain Control Module -- Battery(-)
>>>
>>> the == is 4 wires, 1 for each speed
>>>
>>> If I hook the far side of the relay to ground, the blower blows. The
>>> relay is controlled by both ignition and vent selector, so just making a
>>> permanent connection to ground would leave me with a fully functional
>>> system.
>>>
>>> But before I go with that hack, wondering if I am missing something?
>>>
>>> The PCM is $480+installation required to program it.
>>>
>>> Will a "diagnostic code reader" ($99 from local auto store) tell me if
>>> the PCM is not letting the blower blow?
>>>
>>> Also, $99 gets me "just numeric codes for '96 and up" but $250 get a
>>> 'delux' that works on "all cars" and gives descriptions. the 97 is the
>>> only car I have that has any sort of diag system (like it will do my 68
>>> pickup any good) - and I somehow doubt the delux will really tell me
>>> everything I need to know anyway. any comments?
>>>
>>>
>>> Carl K
>>
>> The PCM has nothing to do with your blower motor. What type of heat/
>> A/C controls do you have ? There are two choices, ATM ( Automatic temp
>> control ) or manual control. The wiring is totally different depending on
>> which one you have.
>
> Manual switches.
>
> I have a 97, this is for a 98:
>
> "The PCM manages air-conditioning compressor and coolant-fan operation,
> but it has to see the correct incoming signals before sending outgoing
> commands. When the climate-control head is switched to A/C-on mode, a
> signal is sent to the PCM. The PCM must also receive a signal from the A/C
> low- and high-prcoolant-fan operationessure switches before it turns on
> the compressor and/or coolant fan. These switches prevent damage to the
> system. I'm not sure what method you used to check for a sufficient charge
> of R-134a refrigerant, but a low charge will kill the signal from the
> low-pressure switch and therefore prevent the system from working. It
> could be a low refrigerant charge, defective PCM, faulty climate-control
> head, one of the pressure switches on the blink, a break in related power,
> or an issue with the ground circuit wiring."
The above info is in reference to an ATC system not a manual system. The
wiring is completely different from one to the other. Also, it talks about
the PCM controlling the A/C compressor and the coolant fan. That is all the
PCM controls and it is the same with either system.
>
> http://trucktrend.com/features/advic...rd_ranger.html
>
> Isn't the "coolant-fan operation" the "blower motor" ?
No. The coolant fan motor is the radiator fan.
>
> I am hoping for something else besides the PCM between the relay and the
> Battery(-), like an relay or some other $20 part.
> C
The PCM does not have anything to do with the blower motor.
From what you stated above:
"Pretty sure this is how my 97 Grand Cherokee is wired: (I may make it to
>>> the library to confirm - Haynes wiring didn't have it.)
>>>
>>> Battery(+) -- 40A fuse -- motor -- resistor pack == switch -- relay --
>>> Powertrain Control Module -- Battery(-)
>>>
That's fairly close. It is actually alot simpler. Bat + -- 40A fuse --
blower motor -- resistor pack -- switch -- Ground.
The blower motor switch uses the resistor pack to vary the resistance on
the ground side of the blower motor to change speeds. For high speed the
resistor is bypassed comepletely.
From your other post, so this is easier to follow. You stated :
>> If I hook the far side of the relay to ground, the blower blows.
and I can control the speed with the switch.
The wiring diagram shows no relay in the circuit at all. Are you shure
that you have a relay ? Were is this relay located ?
07-19-2006, 07:45 PM
#15
Guest
Posts: n/a
Re: PCM not letting heat/AC blower blow?
"Carl K" <carl@personnelware.com> wrote in message
news:Ad-dnScCL541OCPZnZ2dnUVZ_qWdnZ2d@comcast.com...
> Mike wrote:
>> "Carl K" <carl@personnelware.com> wrote in message
>> news:pOydnfaDzraa6iPZnZ2dnUVZ_radnZ2d@comcast.com. ..
>>> Pretty sure this is how my 97 Grand Cherokee is wired: (I may make it to
>>> the library to confirm - Haynes wiring didn't have it.)
>>>
>>> Battery(+) -- 40A fuse -- motor -- resistor pack == switch -- relay --
>>> Powertrain Control Module -- Battery(-)
>>>
>>> the == is 4 wires, 1 for each speed
>>>
>>> If I hook the far side of the relay to ground, the blower blows. The
>>> relay is controlled by both ignition and vent selector, so just making a
>>> permanent connection to ground would leave me with a fully functional
>>> system.
>>>
>>> But before I go with that hack, wondering if I am missing something?
>>>
>>> The PCM is $480+installation required to program it.
>>>
>>> Will a "diagnostic code reader" ($99 from local auto store) tell me if
>>> the PCM is not letting the blower blow?
>>>
>>> Also, $99 gets me "just numeric codes for '96 and up" but $250 get a
>>> 'delux' that works on "all cars" and gives descriptions. the 97 is the
>>> only car I have that has any sort of diag system (like it will do my 68
>>> pickup any good) - and I somehow doubt the delux will really tell me
>>> everything I need to know anyway. any comments?
>>>
>>>
>>> Carl K
>>
>> The PCM has nothing to do with your blower motor. What type of heat/
>> A/C controls do you have ? There are two choices, ATM ( Automatic temp
>> control ) or manual control. The wiring is totally different depending on
>> which one you have.
>
> Manual switches.
>
> I have a 97, this is for a 98:
>
> "The PCM manages air-conditioning compressor and coolant-fan operation,
> but it has to see the correct incoming signals before sending outgoing
> commands. When the climate-control head is switched to A/C-on mode, a
> signal is sent to the PCM. The PCM must also receive a signal from the A/C
> low- and high-prcoolant-fan operationessure switches before it turns on
> the compressor and/or coolant fan. These switches prevent damage to the
> system. I'm not sure what method you used to check for a sufficient charge
> of R-134a refrigerant, but a low charge will kill the signal from the
> low-pressure switch and therefore prevent the system from working. It
> could be a low refrigerant charge, defective PCM, faulty climate-control
> head, one of the pressure switches on the blink, a break in related power,
> or an issue with the ground circuit wiring."
The above info is in reference to an ATC system not a manual system. The
wiring is completely different from one to the other. Also, it talks about
the PCM controlling the A/C compressor and the coolant fan. That is all the
PCM controls and it is the same with either system.
>
> http://trucktrend.com/features/advic...rd_ranger.html
>
> Isn't the "coolant-fan operation" the "blower motor" ?
No. The coolant fan motor is the radiator fan.
>
> I am hoping for something else besides the PCM between the relay and the
> Battery(-), like an relay or some other $20 part.
> C
The PCM does not have anything to do with the blower motor.
From what you stated above:
"Pretty sure this is how my 97 Grand Cherokee is wired: (I may make it to
>>> the library to confirm - Haynes wiring didn't have it.)
>>>
>>> Battery(+) -- 40A fuse -- motor -- resistor pack == switch -- relay --
>>> Powertrain Control Module -- Battery(-)
>>>
That's fairly close. It is actually alot simpler. Bat + -- 40A fuse --
blower motor -- resistor pack -- switch -- Ground.
The blower motor switch uses the resistor pack to vary the resistance on
the ground side of the blower motor to change speeds. For high speed the
resistor is bypassed comepletely.
From your other post, so this is easier to follow. You stated :
>> If I hook the far side of the relay to ground, the blower blows.
and I can control the speed with the switch.
The wiring diagram shows no relay in the circuit at all. Are you shure
that you have a relay ? Were is this relay located ?
07-19-2006, 07:45 PM
#16
Guest
Posts: n/a
Re: PCM not letting heat/AC blower blow?
"Carl K" <carl@personnelware.com> wrote in message
news:Ad-dnScCL541OCPZnZ2dnUVZ_qWdnZ2d@comcast.com...
> Mike wrote:
>> "Carl K" <carl@personnelware.com> wrote in message
>> news:pOydnfaDzraa6iPZnZ2dnUVZ_radnZ2d@comcast.com. ..
>>> Pretty sure this is how my 97 Grand Cherokee is wired: (I may make it to
>>> the library to confirm - Haynes wiring didn't have it.)
>>>
>>> Battery(+) -- 40A fuse -- motor -- resistor pack == switch -- relay --
>>> Powertrain Control Module -- Battery(-)
>>>
>>> the == is 4 wires, 1 for each speed
>>>
>>> If I hook the far side of the relay to ground, the blower blows. The
>>> relay is controlled by both ignition and vent selector, so just making a
>>> permanent connection to ground would leave me with a fully functional
>>> system.
>>>
>>> But before I go with that hack, wondering if I am missing something?
>>>
>>> The PCM is $480+installation required to program it.
>>>
>>> Will a "diagnostic code reader" ($99 from local auto store) tell me if
>>> the PCM is not letting the blower blow?
>>>
>>> Also, $99 gets me "just numeric codes for '96 and up" but $250 get a
>>> 'delux' that works on "all cars" and gives descriptions. the 97 is the
>>> only car I have that has any sort of diag system (like it will do my 68
>>> pickup any good) - and I somehow doubt the delux will really tell me
>>> everything I need to know anyway. any comments?
>>>
>>>
>>> Carl K
>>
>> The PCM has nothing to do with your blower motor. What type of heat/
>> A/C controls do you have ? There are two choices, ATM ( Automatic temp
>> control ) or manual control. The wiring is totally different depending on
>> which one you have.
>
> Manual switches.
>
> I have a 97, this is for a 98:
>
> "The PCM manages air-conditioning compressor and coolant-fan operation,
> but it has to see the correct incoming signals before sending outgoing
> commands. When the climate-control head is switched to A/C-on mode, a
> signal is sent to the PCM. The PCM must also receive a signal from the A/C
> low- and high-prcoolant-fan operationessure switches before it turns on
> the compressor and/or coolant fan. These switches prevent damage to the
> system. I'm not sure what method you used to check for a sufficient charge
> of R-134a refrigerant, but a low charge will kill the signal from the
> low-pressure switch and therefore prevent the system from working. It
> could be a low refrigerant charge, defective PCM, faulty climate-control
> head, one of the pressure switches on the blink, a break in related power,
> or an issue with the ground circuit wiring."
The above info is in reference to an ATC system not a manual system. The
wiring is completely different from one to the other. Also, it talks about
the PCM controlling the A/C compressor and the coolant fan. That is all the
PCM controls and it is the same with either system.
>
> http://trucktrend.com/features/advic...rd_ranger.html
>
> Isn't the "coolant-fan operation" the "blower motor" ?
No. The coolant fan motor is the radiator fan.
>
> I am hoping for something else besides the PCM between the relay and the
> Battery(-), like an relay or some other $20 part.
> C
The PCM does not have anything to do with the blower motor.
From what you stated above:
"Pretty sure this is how my 97 Grand Cherokee is wired: (I may make it to
>>> the library to confirm - Haynes wiring didn't have it.)
>>>
>>> Battery(+) -- 40A fuse -- motor -- resistor pack == switch -- relay --
>>> Powertrain Control Module -- Battery(-)
>>>
That's fairly close. It is actually alot simpler. Bat + -- 40A fuse --
blower motor -- resistor pack -- switch -- Ground.
The blower motor switch uses the resistor pack to vary the resistance on
the ground side of the blower motor to change speeds. For high speed the
resistor is bypassed comepletely.
From your other post, so this is easier to follow. You stated :
>> If I hook the far side of the relay to ground, the blower blows.
and I can control the speed with the switch.
The wiring diagram shows no relay in the circuit at all. Are you shure
that you have a relay ? Were is this relay located ?
07-19-2006, 07:45 PM
#17
Guest
Posts: n/a
Re: PCM not letting heat/AC blower blow?
"Carl K" <carl@personnelware.com> wrote in message
news:Ad-dnScCL541OCPZnZ2dnUVZ_qWdnZ2d@comcast.com...
> Mike wrote:
>> "Carl K" <carl@personnelware.com> wrote in message
>> news:pOydnfaDzraa6iPZnZ2dnUVZ_radnZ2d@comcast.com. ..
>>> Pretty sure this is how my 97 Grand Cherokee is wired: (I may make it to
>>> the library to confirm - Haynes wiring didn't have it.)
>>>
>>> Battery(+) -- 40A fuse -- motor -- resistor pack == switch -- relay --
>>> Powertrain Control Module -- Battery(-)
>>>
>>> the == is 4 wires, 1 for each speed
>>>
>>> If I hook the far side of the relay to ground, the blower blows. The
>>> relay is controlled by both ignition and vent selector, so just making a
>>> permanent connection to ground would leave me with a fully functional
>>> system.
>>>
>>> But before I go with that hack, wondering if I am missing something?
>>>
>>> The PCM is $480+installation required to program it.
>>>
>>> Will a "diagnostic code reader" ($99 from local auto store) tell me if
>>> the PCM is not letting the blower blow?
>>>
>>> Also, $99 gets me "just numeric codes for '96 and up" but $250 get a
>>> 'delux' that works on "all cars" and gives descriptions. the 97 is the
>>> only car I have that has any sort of diag system (like it will do my 68
>>> pickup any good) - and I somehow doubt the delux will really tell me
>>> everything I need to know anyway. any comments?
>>>
>>>
>>> Carl K
>>
>> The PCM has nothing to do with your blower motor. What type of heat/
>> A/C controls do you have ? There are two choices, ATM ( Automatic temp
>> control ) or manual control. The wiring is totally different depending on
>> which one you have.
>
> Manual switches.
>
> I have a 97, this is for a 98:
>
> "The PCM manages air-conditioning compressor and coolant-fan operation,
> but it has to see the correct incoming signals before sending outgoing
> commands. When the climate-control head is switched to A/C-on mode, a
> signal is sent to the PCM. The PCM must also receive a signal from the A/C
> low- and high-prcoolant-fan operationessure switches before it turns on
> the compressor and/or coolant fan. These switches prevent damage to the
> system. I'm not sure what method you used to check for a sufficient charge
> of R-134a refrigerant, but a low charge will kill the signal from the
> low-pressure switch and therefore prevent the system from working. It
> could be a low refrigerant charge, defective PCM, faulty climate-control
> head, one of the pressure switches on the blink, a break in related power,
> or an issue with the ground circuit wiring."
The above info is in reference to an ATC system not a manual system. The
wiring is completely different from one to the other. Also, it talks about
the PCM controlling the A/C compressor and the coolant fan. That is all the
PCM controls and it is the same with either system.
>
> http://trucktrend.com/features/advic...rd_ranger.html
>
> Isn't the "coolant-fan operation" the "blower motor" ?
No. The coolant fan motor is the radiator fan.
>
> I am hoping for something else besides the PCM between the relay and the
> Battery(-), like an relay or some other $20 part.
> C
The PCM does not have anything to do with the blower motor.
From what you stated above:
"Pretty sure this is how my 97 Grand Cherokee is wired: (I may make it to
>>> the library to confirm - Haynes wiring didn't have it.)
>>>
>>> Battery(+) -- 40A fuse -- motor -- resistor pack == switch -- relay --
>>> Powertrain Control Module -- Battery(-)
>>>
That's fairly close. It is actually alot simpler. Bat + -- 40A fuse --
blower motor -- resistor pack -- switch -- Ground.
The blower motor switch uses the resistor pack to vary the resistance on
the ground side of the blower motor to change speeds. For high speed the
resistor is bypassed comepletely.
From your other post, so this is easier to follow. You stated :
>> If I hook the far side of the relay to ground, the blower blows.
and I can control the speed with the switch.
The wiring diagram shows no relay in the circuit at all. Are you shure
that you have a relay ? Were is this relay located ?
07-19-2006, 10:33 PM
#18
Guest
Posts: n/a
Re: PCM not letting heat/AC blower blow?
Mike wrote:
> "Carl K" <carl@personnelware.com> wrote in message
> news:Ad-dnScCL541OCPZnZ2dnUVZ_qWdnZ2d@comcast.com...
>> Mike wrote:
>>> "Carl K" <carl@personnelware.com> wrote in message
>>> news:pOydnfaDzraa6iPZnZ2dnUVZ_radnZ2d@comcast.com. ..
>>>> Pretty sure this is how my 97 Grand Cherokee is wired: (I may make it to
>>>> the library to confirm - Haynes wiring didn't have it.)
>>>>
>>>> Battery(+) -- 40A fuse -- motor -- resistor pack == switch -- relay --
>>>> Powertrain Control Module -- Battery(-)
>>>>
>>>> the == is 4 wires, 1 for each speed
>>>>
>>>> If I hook the far side of the relay to ground, the blower blows. The
>>>> relay is controlled by both ignition and vent selector, so just making a
>>>> permanent connection to ground would leave me with a fully functional
>>>> system.
>>>>
>>>> But before I go with that hack, wondering if I am missing something?
>>>>
>>>> The PCM is $480+installation required to program it.
>>>>
>>>> Will a "diagnostic code reader" ($99 from local auto store) tell me if
>>>> the PCM is not letting the blower blow?
>>>>
>>>> Also, $99 gets me "just numeric codes for '96 and up" but $250 get a
>>>> 'delux' that works on "all cars" and gives descriptions. the 97 is the
>>>> only car I have that has any sort of diag system (like it will do my 68
>>>> pickup any good) - and I somehow doubt the delux will really tell me
>>>> everything I need to know anyway. any comments?
>>>>
>>>>
>>>> Carl K
>>> The PCM has nothing to do with your blower motor. What type of heat/
>>> A/C controls do you have ? There are two choices, ATM ( Automatic temp
>>> control ) or manual control. The wiring is totally different depending on
>>> which one you have.
>> Manual switches.
>>
>> I have a 97, this is for a 98:
>>
>> "The PCM manages air-conditioning compressor and coolant-fan operation,
>> but it has to see the correct incoming signals before sending outgoing
>> commands. When the climate-control head is switched to A/C-on mode, a
>> signal is sent to the PCM. The PCM must also receive a signal from the A/C
>> low- and high-prcoolant-fan operationessure switches before it turns on
>> the compressor and/or coolant fan. These switches prevent damage to the
>> system. I'm not sure what method you used to check for a sufficient charge
>> of R-134a refrigerant, but a low charge will kill the signal from the
>> low-pressure switch and therefore prevent the system from working. It
>> could be a low refrigerant charge, defective PCM, faulty climate-control
>> head, one of the pressure switches on the blink, a break in related power,
>> or an issue with the ground circuit wiring."
>
>
> The above info is in reference to an ATC system not a manual system. The
> wiring is completely different from one to the other. Also, it talks about
> the PCM controlling the A/C compressor and the coolant fan. That is all the
> PCM controls and it is the same with either system.
>
>
>> http://trucktrend.com/features/advic...rd_ranger.html
>>
>> Isn't the "coolant-fan operation" the "blower motor" ?
>
>
> No. The coolant fan motor is the radiator fan.
ah - I was wondering why it was called something other than "blower motor."
>
>> I am hoping for something else besides the PCM between the relay and the
>> Battery(-), like an relay or some other $20 part.
>> C
>
> The PCM does not have anything to do with the blower motor.
>
> From what you stated above:
>
> "Pretty sure this is how my 97 Grand Cherokee is wired: (I may make it to
>>>> the library to confirm - Haynes wiring didn't have it.)
>>>>
>>>> Battery(+) -- 40A fuse -- motor -- resistor pack == switch -- relay --
>>>> Powertrain Control Module -- Battery(-)
>>>>
>
> That's fairly close. It is actually alot simpler. Bat + -- 40A fuse --
> blower motor -- resistor pack -- switch -- Ground.
>
> The blower motor switch uses the resistor pack to vary the resistance on
> the ground side of the blower motor to change speeds. For high speed the
> resistor is bypassed comepletely.
>
>
> From your other post, so this is easier to follow. You stated :
>
>>> If I hook the far side of the relay to ground, the blower blows.
>
> and I can control the speed with the switch.
>
> Good Q - how did that happen?
> The wiring diagram shows no relay in the circuit at all. Are you shure
> that you have a relay ? Were is this relay located ?
>
>
Whoops.
Good Q - how did that happen?
Bat+ -- 40A fuse -- blower motor -- resistor pack == switch --x- relay switch
-y-- PCM? -- Ground.
The relay coil side is driven by the ignition switch and the air flow control
switch (off and 7 on's: max, norm, bi, vent, heat, heat/def, def)
If I ground X, the blower blows and I can adjust the speed with the speed
switch: low to high (no off).
If I ground Y, the blower only blows when the relay is engaged: ignition and air
flow control switch on.
If the far side of the relay was just going to ground, where would the wire
terminate?
The relay is mounted inside the box that the 3 controls are in: fan speed, air
flow and hot/cold. if you look at the back of the box, you can see the 4
connectors, you have to disassemble the box to pull the relay out.
I am hung up on it going to the PCM just because of the XJ wiring diagram I
have. but it is significantly different (like the relay is between the 40A
fuse and the motor) , so it won't surprise me if it just goes to ground.
Carl K
> "Carl K" <carl@personnelware.com> wrote in message
> news:Ad-dnScCL541OCPZnZ2dnUVZ_qWdnZ2d@comcast.com...
>> Mike wrote:
>>> "Carl K" <carl@personnelware.com> wrote in message
>>> news:pOydnfaDzraa6iPZnZ2dnUVZ_radnZ2d@comcast.com. ..
>>>> Pretty sure this is how my 97 Grand Cherokee is wired: (I may make it to
>>>> the library to confirm - Haynes wiring didn't have it.)
>>>>
>>>> Battery(+) -- 40A fuse -- motor -- resistor pack == switch -- relay --
>>>> Powertrain Control Module -- Battery(-)
>>>>
>>>> the == is 4 wires, 1 for each speed
>>>>
>>>> If I hook the far side of the relay to ground, the blower blows. The
>>>> relay is controlled by both ignition and vent selector, so just making a
>>>> permanent connection to ground would leave me with a fully functional
>>>> system.
>>>>
>>>> But before I go with that hack, wondering if I am missing something?
>>>>
>>>> The PCM is $480+installation required to program it.
>>>>
>>>> Will a "diagnostic code reader" ($99 from local auto store) tell me if
>>>> the PCM is not letting the blower blow?
>>>>
>>>> Also, $99 gets me "just numeric codes for '96 and up" but $250 get a
>>>> 'delux' that works on "all cars" and gives descriptions. the 97 is the
>>>> only car I have that has any sort of diag system (like it will do my 68
>>>> pickup any good) - and I somehow doubt the delux will really tell me
>>>> everything I need to know anyway. any comments?
>>>>
>>>>
>>>> Carl K
>>> The PCM has nothing to do with your blower motor. What type of heat/
>>> A/C controls do you have ? There are two choices, ATM ( Automatic temp
>>> control ) or manual control. The wiring is totally different depending on
>>> which one you have.
>> Manual switches.
>>
>> I have a 97, this is for a 98:
>>
>> "The PCM manages air-conditioning compressor and coolant-fan operation,
>> but it has to see the correct incoming signals before sending outgoing
>> commands. When the climate-control head is switched to A/C-on mode, a
>> signal is sent to the PCM. The PCM must also receive a signal from the A/C
>> low- and high-prcoolant-fan operationessure switches before it turns on
>> the compressor and/or coolant fan. These switches prevent damage to the
>> system. I'm not sure what method you used to check for a sufficient charge
>> of R-134a refrigerant, but a low charge will kill the signal from the
>> low-pressure switch and therefore prevent the system from working. It
>> could be a low refrigerant charge, defective PCM, faulty climate-control
>> head, one of the pressure switches on the blink, a break in related power,
>> or an issue with the ground circuit wiring."
>
>
> The above info is in reference to an ATC system not a manual system. The
> wiring is completely different from one to the other. Also, it talks about
> the PCM controlling the A/C compressor and the coolant fan. That is all the
> PCM controls and it is the same with either system.
>
>
>> http://trucktrend.com/features/advic...rd_ranger.html
>>
>> Isn't the "coolant-fan operation" the "blower motor" ?
>
>
> No. The coolant fan motor is the radiator fan.
ah - I was wondering why it was called something other than "blower motor."
>
>> I am hoping for something else besides the PCM between the relay and the
>> Battery(-), like an relay or some other $20 part.
>> C
>
> The PCM does not have anything to do with the blower motor.
>
> From what you stated above:
>
> "Pretty sure this is how my 97 Grand Cherokee is wired: (I may make it to
>>>> the library to confirm - Haynes wiring didn't have it.)
>>>>
>>>> Battery(+) -- 40A fuse -- motor -- resistor pack == switch -- relay --
>>>> Powertrain Control Module -- Battery(-)
>>>>
>
> That's fairly close. It is actually alot simpler. Bat + -- 40A fuse --
> blower motor -- resistor pack -- switch -- Ground.
>
> The blower motor switch uses the resistor pack to vary the resistance on
> the ground side of the blower motor to change speeds. For high speed the
> resistor is bypassed comepletely.
>
>
> From your other post, so this is easier to follow. You stated :
>
>>> If I hook the far side of the relay to ground, the blower blows.
>
> and I can control the speed with the switch.
>
> Good Q - how did that happen?
> The wiring diagram shows no relay in the circuit at all. Are you shure
> that you have a relay ? Were is this relay located ?
>
>
Whoops.
Good Q - how did that happen?
Bat+ -- 40A fuse -- blower motor -- resistor pack == switch --x- relay switch
-y-- PCM? -- Ground.
The relay coil side is driven by the ignition switch and the air flow control
switch (off and 7 on's: max, norm, bi, vent, heat, heat/def, def)
If I ground X, the blower blows and I can adjust the speed with the speed
switch: low to high (no off).
If I ground Y, the blower only blows when the relay is engaged: ignition and air
flow control switch on.
If the far side of the relay was just going to ground, where would the wire
terminate?
The relay is mounted inside the box that the 3 controls are in: fan speed, air
flow and hot/cold. if you look at the back of the box, you can see the 4
connectors, you have to disassemble the box to pull the relay out.
I am hung up on it going to the PCM just because of the XJ wiring diagram I
have. but it is significantly different (like the relay is between the 40A
fuse and the motor) , so it won't surprise me if it just goes to ground.
Carl K
07-19-2006, 10:33 PM
#19
Guest
Posts: n/a
Re: PCM not letting heat/AC blower blow?
Mike wrote:
> "Carl K" <carl@personnelware.com> wrote in message
> news:Ad-dnScCL541OCPZnZ2dnUVZ_qWdnZ2d@comcast.com...
>> Mike wrote:
>>> "Carl K" <carl@personnelware.com> wrote in message
>>> news:pOydnfaDzraa6iPZnZ2dnUVZ_radnZ2d@comcast.com. ..
>>>> Pretty sure this is how my 97 Grand Cherokee is wired: (I may make it to
>>>> the library to confirm - Haynes wiring didn't have it.)
>>>>
>>>> Battery(+) -- 40A fuse -- motor -- resistor pack == switch -- relay --
>>>> Powertrain Control Module -- Battery(-)
>>>>
>>>> the == is 4 wires, 1 for each speed
>>>>
>>>> If I hook the far side of the relay to ground, the blower blows. The
>>>> relay is controlled by both ignition and vent selector, so just making a
>>>> permanent connection to ground would leave me with a fully functional
>>>> system.
>>>>
>>>> But before I go with that hack, wondering if I am missing something?
>>>>
>>>> The PCM is $480+installation required to program it.
>>>>
>>>> Will a "diagnostic code reader" ($99 from local auto store) tell me if
>>>> the PCM is not letting the blower blow?
>>>>
>>>> Also, $99 gets me "just numeric codes for '96 and up" but $250 get a
>>>> 'delux' that works on "all cars" and gives descriptions. the 97 is the
>>>> only car I have that has any sort of diag system (like it will do my 68
>>>> pickup any good) - and I somehow doubt the delux will really tell me
>>>> everything I need to know anyway. any comments?
>>>>
>>>>
>>>> Carl K
>>> The PCM has nothing to do with your blower motor. What type of heat/
>>> A/C controls do you have ? There are two choices, ATM ( Automatic temp
>>> control ) or manual control. The wiring is totally different depending on
>>> which one you have.
>> Manual switches.
>>
>> I have a 97, this is for a 98:
>>
>> "The PCM manages air-conditioning compressor and coolant-fan operation,
>> but it has to see the correct incoming signals before sending outgoing
>> commands. When the climate-control head is switched to A/C-on mode, a
>> signal is sent to the PCM. The PCM must also receive a signal from the A/C
>> low- and high-prcoolant-fan operationessure switches before it turns on
>> the compressor and/or coolant fan. These switches prevent damage to the
>> system. I'm not sure what method you used to check for a sufficient charge
>> of R-134a refrigerant, but a low charge will kill the signal from the
>> low-pressure switch and therefore prevent the system from working. It
>> could be a low refrigerant charge, defective PCM, faulty climate-control
>> head, one of the pressure switches on the blink, a break in related power,
>> or an issue with the ground circuit wiring."
>
>
> The above info is in reference to an ATC system not a manual system. The
> wiring is completely different from one to the other. Also, it talks about
> the PCM controlling the A/C compressor and the coolant fan. That is all the
> PCM controls and it is the same with either system.
>
>
>> http://trucktrend.com/features/advic...rd_ranger.html
>>
>> Isn't the "coolant-fan operation" the "blower motor" ?
>
>
> No. The coolant fan motor is the radiator fan.
ah - I was wondering why it was called something other than "blower motor."
>
>> I am hoping for something else besides the PCM between the relay and the
>> Battery(-), like an relay or some other $20 part.
>> C
>
> The PCM does not have anything to do with the blower motor.
>
> From what you stated above:
>
> "Pretty sure this is how my 97 Grand Cherokee is wired: (I may make it to
>>>> the library to confirm - Haynes wiring didn't have it.)
>>>>
>>>> Battery(+) -- 40A fuse -- motor -- resistor pack == switch -- relay --
>>>> Powertrain Control Module -- Battery(-)
>>>>
>
> That's fairly close. It is actually alot simpler. Bat + -- 40A fuse --
> blower motor -- resistor pack -- switch -- Ground.
>
> The blower motor switch uses the resistor pack to vary the resistance on
> the ground side of the blower motor to change speeds. For high speed the
> resistor is bypassed comepletely.
>
>
> From your other post, so this is easier to follow. You stated :
>
>>> If I hook the far side of the relay to ground, the blower blows.
>
> and I can control the speed with the switch.
>
> Good Q - how did that happen?
> The wiring diagram shows no relay in the circuit at all. Are you shure
> that you have a relay ? Were is this relay located ?
>
>
Whoops.
Good Q - how did that happen?
Bat+ -- 40A fuse -- blower motor -- resistor pack == switch --x- relay switch
-y-- PCM? -- Ground.
The relay coil side is driven by the ignition switch and the air flow control
switch (off and 7 on's: max, norm, bi, vent, heat, heat/def, def)
If I ground X, the blower blows and I can adjust the speed with the speed
switch: low to high (no off).
If I ground Y, the blower only blows when the relay is engaged: ignition and air
flow control switch on.
If the far side of the relay was just going to ground, where would the wire
terminate?
The relay is mounted inside the box that the 3 controls are in: fan speed, air
flow and hot/cold. if you look at the back of the box, you can see the 4
connectors, you have to disassemble the box to pull the relay out.
I am hung up on it going to the PCM just because of the XJ wiring diagram I
have. but it is significantly different (like the relay is between the 40A
fuse and the motor) , so it won't surprise me if it just goes to ground.
Carl K
> "Carl K" <carl@personnelware.com> wrote in message
> news:Ad-dnScCL541OCPZnZ2dnUVZ_qWdnZ2d@comcast.com...
>> Mike wrote:
>>> "Carl K" <carl@personnelware.com> wrote in message
>>> news:pOydnfaDzraa6iPZnZ2dnUVZ_radnZ2d@comcast.com. ..
>>>> Pretty sure this is how my 97 Grand Cherokee is wired: (I may make it to
>>>> the library to confirm - Haynes wiring didn't have it.)
>>>>
>>>> Battery(+) -- 40A fuse -- motor -- resistor pack == switch -- relay --
>>>> Powertrain Control Module -- Battery(-)
>>>>
>>>> the == is 4 wires, 1 for each speed
>>>>
>>>> If I hook the far side of the relay to ground, the blower blows. The
>>>> relay is controlled by both ignition and vent selector, so just making a
>>>> permanent connection to ground would leave me with a fully functional
>>>> system.
>>>>
>>>> But before I go with that hack, wondering if I am missing something?
>>>>
>>>> The PCM is $480+installation required to program it.
>>>>
>>>> Will a "diagnostic code reader" ($99 from local auto store) tell me if
>>>> the PCM is not letting the blower blow?
>>>>
>>>> Also, $99 gets me "just numeric codes for '96 and up" but $250 get a
>>>> 'delux' that works on "all cars" and gives descriptions. the 97 is the
>>>> only car I have that has any sort of diag system (like it will do my 68
>>>> pickup any good) - and I somehow doubt the delux will really tell me
>>>> everything I need to know anyway. any comments?
>>>>
>>>>
>>>> Carl K
>>> The PCM has nothing to do with your blower motor. What type of heat/
>>> A/C controls do you have ? There are two choices, ATM ( Automatic temp
>>> control ) or manual control. The wiring is totally different depending on
>>> which one you have.
>> Manual switches.
>>
>> I have a 97, this is for a 98:
>>
>> "The PCM manages air-conditioning compressor and coolant-fan operation,
>> but it has to see the correct incoming signals before sending outgoing
>> commands. When the climate-control head is switched to A/C-on mode, a
>> signal is sent to the PCM. The PCM must also receive a signal from the A/C
>> low- and high-prcoolant-fan operationessure switches before it turns on
>> the compressor and/or coolant fan. These switches prevent damage to the
>> system. I'm not sure what method you used to check for a sufficient charge
>> of R-134a refrigerant, but a low charge will kill the signal from the
>> low-pressure switch and therefore prevent the system from working. It
>> could be a low refrigerant charge, defective PCM, faulty climate-control
>> head, one of the pressure switches on the blink, a break in related power,
>> or an issue with the ground circuit wiring."
>
>
> The above info is in reference to an ATC system not a manual system. The
> wiring is completely different from one to the other. Also, it talks about
> the PCM controlling the A/C compressor and the coolant fan. That is all the
> PCM controls and it is the same with either system.
>
>
>> http://trucktrend.com/features/advic...rd_ranger.html
>>
>> Isn't the "coolant-fan operation" the "blower motor" ?
>
>
> No. The coolant fan motor is the radiator fan.
ah - I was wondering why it was called something other than "blower motor."
>
>> I am hoping for something else besides the PCM between the relay and the
>> Battery(-), like an relay or some other $20 part.
>> C
>
> The PCM does not have anything to do with the blower motor.
>
> From what you stated above:
>
> "Pretty sure this is how my 97 Grand Cherokee is wired: (I may make it to
>>>> the library to confirm - Haynes wiring didn't have it.)
>>>>
>>>> Battery(+) -- 40A fuse -- motor -- resistor pack == switch -- relay --
>>>> Powertrain Control Module -- Battery(-)
>>>>
>
> That's fairly close. It is actually alot simpler. Bat + -- 40A fuse --
> blower motor -- resistor pack -- switch -- Ground.
>
> The blower motor switch uses the resistor pack to vary the resistance on
> the ground side of the blower motor to change speeds. For high speed the
> resistor is bypassed comepletely.
>
>
> From your other post, so this is easier to follow. You stated :
>
>>> If I hook the far side of the relay to ground, the blower blows.
>
> and I can control the speed with the switch.
>
> Good Q - how did that happen?
> The wiring diagram shows no relay in the circuit at all. Are you shure
> that you have a relay ? Were is this relay located ?
>
>
Whoops.
Good Q - how did that happen?
Bat+ -- 40A fuse -- blower motor -- resistor pack == switch --x- relay switch
-y-- PCM? -- Ground.
The relay coil side is driven by the ignition switch and the air flow control
switch (off and 7 on's: max, norm, bi, vent, heat, heat/def, def)
If I ground X, the blower blows and I can adjust the speed with the speed
switch: low to high (no off).
If I ground Y, the blower only blows when the relay is engaged: ignition and air
flow control switch on.
If the far side of the relay was just going to ground, where would the wire
terminate?
The relay is mounted inside the box that the 3 controls are in: fan speed, air
flow and hot/cold. if you look at the back of the box, you can see the 4
connectors, you have to disassemble the box to pull the relay out.
I am hung up on it going to the PCM just because of the XJ wiring diagram I
have. but it is significantly different (like the relay is between the 40A
fuse and the motor) , so it won't surprise me if it just goes to ground.
Carl K
07-19-2006, 10:33 PM
#20
Guest
Posts: n/a
Re: PCM not letting heat/AC blower blow?
Mike wrote:
> "Carl K" <carl@personnelware.com> wrote in message
> news:Ad-dnScCL541OCPZnZ2dnUVZ_qWdnZ2d@comcast.com...
>> Mike wrote:
>>> "Carl K" <carl@personnelware.com> wrote in message
>>> news:pOydnfaDzraa6iPZnZ2dnUVZ_radnZ2d@comcast.com. ..
>>>> Pretty sure this is how my 97 Grand Cherokee is wired: (I may make it to
>>>> the library to confirm - Haynes wiring didn't have it.)
>>>>
>>>> Battery(+) -- 40A fuse -- motor -- resistor pack == switch -- relay --
>>>> Powertrain Control Module -- Battery(-)
>>>>
>>>> the == is 4 wires, 1 for each speed
>>>>
>>>> If I hook the far side of the relay to ground, the blower blows. The
>>>> relay is controlled by both ignition and vent selector, so just making a
>>>> permanent connection to ground would leave me with a fully functional
>>>> system.
>>>>
>>>> But before I go with that hack, wondering if I am missing something?
>>>>
>>>> The PCM is $480+installation required to program it.
>>>>
>>>> Will a "diagnostic code reader" ($99 from local auto store) tell me if
>>>> the PCM is not letting the blower blow?
>>>>
>>>> Also, $99 gets me "just numeric codes for '96 and up" but $250 get a
>>>> 'delux' that works on "all cars" and gives descriptions. the 97 is the
>>>> only car I have that has any sort of diag system (like it will do my 68
>>>> pickup any good) - and I somehow doubt the delux will really tell me
>>>> everything I need to know anyway. any comments?
>>>>
>>>>
>>>> Carl K
>>> The PCM has nothing to do with your blower motor. What type of heat/
>>> A/C controls do you have ? There are two choices, ATM ( Automatic temp
>>> control ) or manual control. The wiring is totally different depending on
>>> which one you have.
>> Manual switches.
>>
>> I have a 97, this is for a 98:
>>
>> "The PCM manages air-conditioning compressor and coolant-fan operation,
>> but it has to see the correct incoming signals before sending outgoing
>> commands. When the climate-control head is switched to A/C-on mode, a
>> signal is sent to the PCM. The PCM must also receive a signal from the A/C
>> low- and high-prcoolant-fan operationessure switches before it turns on
>> the compressor and/or coolant fan. These switches prevent damage to the
>> system. I'm not sure what method you used to check for a sufficient charge
>> of R-134a refrigerant, but a low charge will kill the signal from the
>> low-pressure switch and therefore prevent the system from working. It
>> could be a low refrigerant charge, defective PCM, faulty climate-control
>> head, one of the pressure switches on the blink, a break in related power,
>> or an issue with the ground circuit wiring."
>
>
> The above info is in reference to an ATC system not a manual system. The
> wiring is completely different from one to the other. Also, it talks about
> the PCM controlling the A/C compressor and the coolant fan. That is all the
> PCM controls and it is the same with either system.
>
>
>> http://trucktrend.com/features/advic...rd_ranger.html
>>
>> Isn't the "coolant-fan operation" the "blower motor" ?
>
>
> No. The coolant fan motor is the radiator fan.
ah - I was wondering why it was called something other than "blower motor."
>
>> I am hoping for something else besides the PCM between the relay and the
>> Battery(-), like an relay or some other $20 part.
>> C
>
> The PCM does not have anything to do with the blower motor.
>
> From what you stated above:
>
> "Pretty sure this is how my 97 Grand Cherokee is wired: (I may make it to
>>>> the library to confirm - Haynes wiring didn't have it.)
>>>>
>>>> Battery(+) -- 40A fuse -- motor -- resistor pack == switch -- relay --
>>>> Powertrain Control Module -- Battery(-)
>>>>
>
> That's fairly close. It is actually alot simpler. Bat + -- 40A fuse --
> blower motor -- resistor pack -- switch -- Ground.
>
> The blower motor switch uses the resistor pack to vary the resistance on
> the ground side of the blower motor to change speeds. For high speed the
> resistor is bypassed comepletely.
>
>
> From your other post, so this is easier to follow. You stated :
>
>>> If I hook the far side of the relay to ground, the blower blows.
>
> and I can control the speed with the switch.
>
> Good Q - how did that happen?
> The wiring diagram shows no relay in the circuit at all. Are you shure
> that you have a relay ? Were is this relay located ?
>
>
Whoops.
Good Q - how did that happen?
Bat+ -- 40A fuse -- blower motor -- resistor pack == switch --x- relay switch
-y-- PCM? -- Ground.
The relay coil side is driven by the ignition switch and the air flow control
switch (off and 7 on's: max, norm, bi, vent, heat, heat/def, def)
If I ground X, the blower blows and I can adjust the speed with the speed
switch: low to high (no off).
If I ground Y, the blower only blows when the relay is engaged: ignition and air
flow control switch on.
If the far side of the relay was just going to ground, where would the wire
terminate?
The relay is mounted inside the box that the 3 controls are in: fan speed, air
flow and hot/cold. if you look at the back of the box, you can see the 4
connectors, you have to disassemble the box to pull the relay out.
I am hung up on it going to the PCM just because of the XJ wiring diagram I
have. but it is significantly different (like the relay is between the 40A
fuse and the motor) , so it won't surprise me if it just goes to ground.
Carl K
> "Carl K" <carl@personnelware.com> wrote in message
> news:Ad-dnScCL541OCPZnZ2dnUVZ_qWdnZ2d@comcast.com...
>> Mike wrote:
>>> "Carl K" <carl@personnelware.com> wrote in message
>>> news:pOydnfaDzraa6iPZnZ2dnUVZ_radnZ2d@comcast.com. ..
>>>> Pretty sure this is how my 97 Grand Cherokee is wired: (I may make it to
>>>> the library to confirm - Haynes wiring didn't have it.)
>>>>
>>>> Battery(+) -- 40A fuse -- motor -- resistor pack == switch -- relay --
>>>> Powertrain Control Module -- Battery(-)
>>>>
>>>> the == is 4 wires, 1 for each speed
>>>>
>>>> If I hook the far side of the relay to ground, the blower blows. The
>>>> relay is controlled by both ignition and vent selector, so just making a
>>>> permanent connection to ground would leave me with a fully functional
>>>> system.
>>>>
>>>> But before I go with that hack, wondering if I am missing something?
>>>>
>>>> The PCM is $480+installation required to program it.
>>>>
>>>> Will a "diagnostic code reader" ($99 from local auto store) tell me if
>>>> the PCM is not letting the blower blow?
>>>>
>>>> Also, $99 gets me "just numeric codes for '96 and up" but $250 get a
>>>> 'delux' that works on "all cars" and gives descriptions. the 97 is the
>>>> only car I have that has any sort of diag system (like it will do my 68
>>>> pickup any good) - and I somehow doubt the delux will really tell me
>>>> everything I need to know anyway. any comments?
>>>>
>>>>
>>>> Carl K
>>> The PCM has nothing to do with your blower motor. What type of heat/
>>> A/C controls do you have ? There are two choices, ATM ( Automatic temp
>>> control ) or manual control. The wiring is totally different depending on
>>> which one you have.
>> Manual switches.
>>
>> I have a 97, this is for a 98:
>>
>> "The PCM manages air-conditioning compressor and coolant-fan operation,
>> but it has to see the correct incoming signals before sending outgoing
>> commands. When the climate-control head is switched to A/C-on mode, a
>> signal is sent to the PCM. The PCM must also receive a signal from the A/C
>> low- and high-prcoolant-fan operationessure switches before it turns on
>> the compressor and/or coolant fan. These switches prevent damage to the
>> system. I'm not sure what method you used to check for a sufficient charge
>> of R-134a refrigerant, but a low charge will kill the signal from the
>> low-pressure switch and therefore prevent the system from working. It
>> could be a low refrigerant charge, defective PCM, faulty climate-control
>> head, one of the pressure switches on the blink, a break in related power,
>> or an issue with the ground circuit wiring."
>
>
> The above info is in reference to an ATC system not a manual system. The
> wiring is completely different from one to the other. Also, it talks about
> the PCM controlling the A/C compressor and the coolant fan. That is all the
> PCM controls and it is the same with either system.
>
>
>> http://trucktrend.com/features/advic...rd_ranger.html
>>
>> Isn't the "coolant-fan operation" the "blower motor" ?
>
>
> No. The coolant fan motor is the radiator fan.
ah - I was wondering why it was called something other than "blower motor."
>
>> I am hoping for something else besides the PCM between the relay and the
>> Battery(-), like an relay or some other $20 part.
>> C
>
> The PCM does not have anything to do with the blower motor.
>
> From what you stated above:
>
> "Pretty sure this is how my 97 Grand Cherokee is wired: (I may make it to
>>>> the library to confirm - Haynes wiring didn't have it.)
>>>>
>>>> Battery(+) -- 40A fuse -- motor -- resistor pack == switch -- relay --
>>>> Powertrain Control Module -- Battery(-)
>>>>
>
> That's fairly close. It is actually alot simpler. Bat + -- 40A fuse --
> blower motor -- resistor pack -- switch -- Ground.
>
> The blower motor switch uses the resistor pack to vary the resistance on
> the ground side of the blower motor to change speeds. For high speed the
> resistor is bypassed comepletely.
>
>
> From your other post, so this is easier to follow. You stated :
>
>>> If I hook the far side of the relay to ground, the blower blows.
>
> and I can control the speed with the switch.
>
> Good Q - how did that happen?
> The wiring diagram shows no relay in the circuit at all. Are you shure
> that you have a relay ? Were is this relay located ?
>
>
Whoops.
Good Q - how did that happen?
Bat+ -- 40A fuse -- blower motor -- resistor pack == switch --x- relay switch
-y-- PCM? -- Ground.
The relay coil side is driven by the ignition switch and the air flow control
switch (off and 7 on's: max, norm, bi, vent, heat, heat/def, def)
If I ground X, the blower blows and I can adjust the speed with the speed
switch: low to high (no off).
If I ground Y, the blower only blows when the relay is engaged: ignition and air
flow control switch on.
If the far side of the relay was just going to ground, where would the wire
terminate?
The relay is mounted inside the box that the 3 controls are in: fan speed, air
flow and hot/cold. if you look at the back of the box, you can see the 4
connectors, you have to disassemble the box to pull the relay out.
I am hung up on it going to the PCM just because of the XJ wiring diagram I
have. but it is significantly different (like the relay is between the 40A
fuse and the motor) , so it won't surprise me if it just goes to ground.
Carl K
