PCM not letting heat/AC blower blow?
 

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

Re: PCM not letting heat/AC blower blow?
 

Perhaps someone on the board has a ZJ manual. 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.


"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

Re: PCM not letting heat/AC blower blow?
 

Perhaps someone on the board has a ZJ manual. 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.


"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

Re: PCM not letting heat/AC blower blow?
 

Perhaps someone on the board has a ZJ manual. 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.


"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

Re: PCM not letting heat/AC blower blow?
 

"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.

Re: PCM not letting heat/AC blower blow?
 

"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.

Re: PCM not letting heat/AC blower blow?
 

"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.

Re: PCM not letting heat/AC blower blow?
 

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."

http://trucktrend.com/features/advic...rd_ranger.html

Isn't the "coolant-fan operation" the "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

Re: PCM not letting heat/AC blower blow?
 

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."

http://trucktrend.com/features/advic...rd_ranger.html

Isn't the "coolant-fan operation" the "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

Re: PCM not letting heat/AC blower blow?
 

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."

http://trucktrend.com/features/advic...rd_ranger.html

Isn't the "coolant-fan operation" the "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