Help, A/C blower motor won't turn off
I have a strange problem in my 94 Grand Cherokee Limited. The other
day I turned the car off and the a/c blower motor (fan) kept running even after I took the key out. I had to pull the fuse to shut it off. The a/c and heater seem to work ok, it's just that the fan won't turn off. I took it to a local mechanic who said I need a new HVAC control head. The dealer has to order it, and it costs $700! Can it really be that big of a problem to fix a blower motor that won't shut off? I'm now popping the hood and putting the fuse in before I drive, then pulling the fuse when I'm done. For $700, I'm thinking of building some kind of switch that runs from the fuse to outside the hood so I don't have to pop the hood. Any ideas? |
Re: Help, A/C blower motor won't turn off
Ummm...
Maybe the sensor has failed? Try a multimeter on it to see if it has a connection when cold, if so replace it. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's np6 wrote: > > I have a strange problem in my 94 Grand Cherokee Limited. The other > day I turned the car off and the a/c blower motor (fan) kept running > even after I took the key out. I had to pull the fuse to shut it off. > The a/c and heater seem to work ok, it's just that the fan won't turn > off. I took it to a local mechanic who said I need a new HVAC control > head. The dealer has to order it, and it costs $700! Can it really > be that big of a problem to fix a blower motor that won't shut off? > I'm now popping the hood and putting the fuse in before I drive, then > pulling the fuse when I'm done. For $700, I'm thinking of building > some kind of switch that runs from the fuse to outside the hood so I > don't have to pop the hood. Any ideas? |
Re: Help, A/C blower motor won't turn off
Ummm...
Maybe the sensor has failed? Try a multimeter on it to see if it has a connection when cold, if so replace it. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's np6 wrote: > > I have a strange problem in my 94 Grand Cherokee Limited. The other > day I turned the car off and the a/c blower motor (fan) kept running > even after I took the key out. I had to pull the fuse to shut it off. > The a/c and heater seem to work ok, it's just that the fan won't turn > off. I took it to a local mechanic who said I need a new HVAC control > head. The dealer has to order it, and it costs $700! Can it really > be that big of a problem to fix a blower motor that won't shut off? > I'm now popping the hood and putting the fuse in before I drive, then > pulling the fuse when I'm done. For $700, I'm thinking of building > some kind of switch that runs from the fuse to outside the hood so I > don't have to pop the hood. Any ideas? |
Re: Help, A/C blower motor won't turn off
np6 did pass the time by typing: > I have a strange problem in my 94 Grand Cherokee Limited. The other > day I turned the car off and the a/c blower motor (fan) kept running > even after I took the key out. I had to pull the fuse to shut it off. Tell the mechanic to get bent. :) From your description and the base Limited, prolly the auto. So let's start there. I'm betting you have a stuck blower motor relay. That's the most likely failure point. Problem is I think the relay is in the control head. Should be real close to the fan speed switch. Follow the trace back from pin 4. Give it a good thwack with a mallet.. er.. tap it a couple of times it might free up. This schematic is very poor on that module, it almost looks like a replacable 5 pin style relay, like a fog relay. My scanner is down, but if you want the schematic just post a reply with "DougW" in the subject line and I'll catch it easier. -- -- DougW -- 93 ZJ 4.0 http://members.cox.net/wilsond HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors |
Re: Help, A/C blower motor won't turn off
np6 did pass the time by typing: > I have a strange problem in my 94 Grand Cherokee Limited. The other > day I turned the car off and the a/c blower motor (fan) kept running > even after I took the key out. I had to pull the fuse to shut it off. Tell the mechanic to get bent. :) From your description and the base Limited, prolly the auto. So let's start there. I'm betting you have a stuck blower motor relay. That's the most likely failure point. Problem is I think the relay is in the control head. Should be real close to the fan speed switch. Follow the trace back from pin 4. Give it a good thwack with a mallet.. er.. tap it a couple of times it might free up. This schematic is very poor on that module, it almost looks like a replacable 5 pin style relay, like a fog relay. My scanner is down, but if you want the schematic just post a reply with "DougW" in the subject line and I'll catch it easier. -- -- DougW -- 93 ZJ 4.0 http://members.cox.net/wilsond HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors |
Re: Help, A/C blower motor won't turn off
Approximately 9/24/03 15:38, np6 uttered for posterity:
> I have a strange problem in my 94 Grand Cherokee Limited. The other > day I turned the car off and the a/c blower motor (fan) kept running > even after I took the key out. I had to pull the fuse to shut it off. > The a/c and heater seem to work ok, it's just that the fan won't turn > off. I took it to a local mechanic who said I need a new HVAC control > head. The dealer has to order it, and it costs $700! Can it really > be that big of a problem to fix a blower motor that won't shut off? > I'm now popping the hood and putting the fuse in before I drive, then > pulling the fuse when I'm done. For $700, I'm thinking of building > some kind of switch that runs from the fuse to outside the hood so I > don't have to pop the hood. Any ideas? The blower motor is controlled by the ATC controls with speed feedback. You may want to disconnect the battery as it resets the control completely. This *could* be as trivial as the high speed relay. With the fuse in, turn it on, then turn the motor off. Then pull the A/C fault codes. Push AC and RECIRC at the same time. While doing this, rotate the Temp knob one click Clockwise. This should light all indicators as long if you keep your fingers on the AC/RECIRC. Take your fingers off the AC/RECIRC and the display should go to 00, ready to pull codes. Push *either* the AC or RECIRC but not both. The little stickman appears indicating you are now in Diagnostic Mode. If the display stays at 00, the thing doesn't *think* the ATC module is bad. Push the same button AC *or* RECIRC to step codes. If you see fault 25 or 29, the ATC is bad and the rest of any codes are bogus. Code 08 would indicate motor feedback is too high, possibly not the ATC. 12 means the fan control knob is bad. 16 means not enough motor feedback. 40 means at some point the feedback was too high but not at the present. 48 is historical feedback too low. 61 means the ATC was bad but thinks it is ok now. To clear codes, push AC *or* RECIRC and hold for 3-4 seconds until 2 bars appear on the display. Only clears codes 33 and higher. You can pull detailed status by starting all over, push AC and RECIRC, one click CW. This should turn on the stick man and set to 00 or an uncleared fault code. Step the tests by rotating the knob CW. OC is open ckt, SC is short. As you step the display with the knob, to read the inputs, press either AC or RECIRC. To actually test the outputs, go back to Diag Mode with the AC/RECIRC trick and one CW click. Then select the test you want to run by turning the Temp Knob CW and when it displays the number you want, push the AC button to see the result. Test No. What is checked Display ------- --------------- ------------------------- 01 Blower Ctl Switch ?, OC, SC, 00-255 02 Blower Feedback ? 00-255 03 Blower Speed 00-255 04 Hi Speed Relay 00= off 01= on If you push the RECIRC button during these, the value will step and the motor should speed up/down. And your warranty on this advice is roughly the same as you paid for it. |
Re: Help, A/C blower motor won't turn off
Approximately 9/24/03 15:38, np6 uttered for posterity:
> I have a strange problem in my 94 Grand Cherokee Limited. The other > day I turned the car off and the a/c blower motor (fan) kept running > even after I took the key out. I had to pull the fuse to shut it off. > The a/c and heater seem to work ok, it's just that the fan won't turn > off. I took it to a local mechanic who said I need a new HVAC control > head. The dealer has to order it, and it costs $700! Can it really > be that big of a problem to fix a blower motor that won't shut off? > I'm now popping the hood and putting the fuse in before I drive, then > pulling the fuse when I'm done. For $700, I'm thinking of building > some kind of switch that runs from the fuse to outside the hood so I > don't have to pop the hood. Any ideas? The blower motor is controlled by the ATC controls with speed feedback. You may want to disconnect the battery as it resets the control completely. This *could* be as trivial as the high speed relay. With the fuse in, turn it on, then turn the motor off. Then pull the A/C fault codes. Push AC and RECIRC at the same time. While doing this, rotate the Temp knob one click Clockwise. This should light all indicators as long if you keep your fingers on the AC/RECIRC. Take your fingers off the AC/RECIRC and the display should go to 00, ready to pull codes. Push *either* the AC or RECIRC but not both. The little stickman appears indicating you are now in Diagnostic Mode. If the display stays at 00, the thing doesn't *think* the ATC module is bad. Push the same button AC *or* RECIRC to step codes. If you see fault 25 or 29, the ATC is bad and the rest of any codes are bogus. Code 08 would indicate motor feedback is too high, possibly not the ATC. 12 means the fan control knob is bad. 16 means not enough motor feedback. 40 means at some point the feedback was too high but not at the present. 48 is historical feedback too low. 61 means the ATC was bad but thinks it is ok now. To clear codes, push AC *or* RECIRC and hold for 3-4 seconds until 2 bars appear on the display. Only clears codes 33 and higher. You can pull detailed status by starting all over, push AC and RECIRC, one click CW. This should turn on the stick man and set to 00 or an uncleared fault code. Step the tests by rotating the knob CW. OC is open ckt, SC is short. As you step the display with the knob, to read the inputs, press either AC or RECIRC. To actually test the outputs, go back to Diag Mode with the AC/RECIRC trick and one CW click. Then select the test you want to run by turning the Temp Knob CW and when it displays the number you want, push the AC button to see the result. Test No. What is checked Display ------- --------------- ------------------------- 01 Blower Ctl Switch ?, OC, SC, 00-255 02 Blower Feedback ? 00-255 03 Blower Speed 00-255 04 Hi Speed Relay 00= off 01= on If you push the RECIRC button during these, the value will step and the motor should speed up/down. And your warranty on this advice is roughly the same as you paid for it. |
Re: Help, A/C blower motor won't turn off
Approximately 9/24/03 15:55, DougW uttered for posterity:
> np6 did pass the time by typing: >> I have a strange problem in my 94 Grand Cherokee Limited. The other >> day I turned the car off and the a/c blower motor (fan) kept running >> even after I took the key out. I had to pull the fuse to shut it off. > > > Tell the mechanic to get bent. :) > > From your description and the base Limited, prolly the auto. So let's > start there. > > I'm betting you have a stuck blower motor relay. That's the most > likely failure point. Note that this relay ain't thar unless the unit has ATC. And caution that this is from a 95 FSM, so YMMV. Fuse 11 goes to the high speed relay. If the relay is on, it feeds a full battery voltage to the motor. If the relay is off, the motor speed is controlled by battery voltage being fed to the motor thru the Blower Power Module, which could also be bad. Variable speed is controlled by the BlowerPowerModule which gets its feed from the ATC controller. The Blower Power Module is allegedly along the right side of the Instrument Panel, fairly near the Auto Temp Controls on that panel. The High Speed relay is located along the right hand side of the HVAC under the dash. It gets a one-line feed from the Auto Temp Controller. Unfortunately neither the FSM nor the Body Diag has any better location info or pictures or even remove and repair for those two items. > > Problem is I think the relay is in the control head. Should > be real close to the fan speed switch. Follow the trace back from > pin 4. Give it a good thwack with a mallet.. er.. tap it a couple of times > it might free up. > > This schematic is very poor on that module, it almost looks like a > replacable 5 pin style relay, like a fog relay. > > My scanner is down, but if you want the schematic just post a reply > with "DougW" in the subject line and I'll catch it easier. > > |
Re: Help, A/C blower motor won't turn off
Approximately 9/24/03 15:55, DougW uttered for posterity:
> np6 did pass the time by typing: >> I have a strange problem in my 94 Grand Cherokee Limited. The other >> day I turned the car off and the a/c blower motor (fan) kept running >> even after I took the key out. I had to pull the fuse to shut it off. > > > Tell the mechanic to get bent. :) > > From your description and the base Limited, prolly the auto. So let's > start there. > > I'm betting you have a stuck blower motor relay. That's the most > likely failure point. Note that this relay ain't thar unless the unit has ATC. And caution that this is from a 95 FSM, so YMMV. Fuse 11 goes to the high speed relay. If the relay is on, it feeds a full battery voltage to the motor. If the relay is off, the motor speed is controlled by battery voltage being fed to the motor thru the Blower Power Module, which could also be bad. Variable speed is controlled by the BlowerPowerModule which gets its feed from the ATC controller. The Blower Power Module is allegedly along the right side of the Instrument Panel, fairly near the Auto Temp Controls on that panel. The High Speed relay is located along the right hand side of the HVAC under the dash. It gets a one-line feed from the Auto Temp Controller. Unfortunately neither the FSM nor the Body Diag has any better location info or pictures or even remove and repair for those two items. > > Problem is I think the relay is in the control head. Should > be real close to the fan speed switch. Follow the trace back from > pin 4. Give it a good thwack with a mallet.. er.. tap it a couple of times > it might free up. > > This schematic is very poor on that module, it almost looks like a > replacable 5 pin style relay, like a fog relay. > > My scanner is down, but if you want the schematic just post a reply > with "DougW" in the subject line and I'll catch it easier. > > |
Re: Help, A/C blower motor won't turn off
http://www.----------.com/blower.pdf
God Bless America, ßill O|||||||O mailto:-------------------- np6 wrote: > > I have a strange problem in my 94 Grand Cherokee Limited. The other > day I turned the car off and the a/c blower motor (fan) kept running > even after I took the key out. I had to pull the fuse to shut it off. > The a/c and heater seem to work ok, it's just that the fan won't turn > off. I took it to a local mechanic who said I need a new HVAC control > head. The dealer has to order it, and it costs $700! Can it really > be that big of a problem to fix a blower motor that won't shut off? > I'm now popping the hood and putting the fuse in before I drive, then > pulling the fuse when I'm done. For $700, I'm thinking of building > some kind of switch that runs from the fuse to outside the hood so I > don't have to pop the hood. Any ideas? |
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