A/C switch
Thread Starter
Intermediate
Joined: Aug 2012
Posts: 29
Likes: 0
From: Hondo TX
A/C switch
I have a 1995 C4 Coupe with 90,000 miles. In the last week I have had trouble with the fan switch. I always push auto and the fan comes on and I set the temperature. Now some times the fan comes on and some time it doesn't. Is there a relay that controls the fan. Also the outside temp will start going down and back up went down to -10 then back to 80, where is the sensor for the outside temperature. The fan problem just started the outside temp is a old problem I just put up with. This is a very nice original car in near perfect condition and I want to keep it that way.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
The fan is controlled by the BCM (Blower Control Module), which is mounted on the top of the evaporator housing. In my case the fan sometimes worked and sometimes didn't. It turned out to be corroded pins in the BCM connectors.
The outside temperature sensor is mounted on the frame rail in front of the radiator on the passenger side. You have to look under the front of the car to see it.
The outside temperature sensor is mounted on the frame rail in front of the radiator on the passenger side. You have to look under the front of the car to see it.
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 206
From: Orlando FL
Some added suggestions.
The control head in the dash sometimes has dirty contacts and can be cleaned. The unit does have to come out of the car, disassembled and connector board pins and buttons cleaned. There are several threads on doing this procedure.
This is a common repair procedure.
There is also a possibility the programmer might be going bad. It can have different symptoms. No control over the buttons, LEDs not lit, stuck on a certain button and no temperature display but a back light.
What has got my attention is you temperature display problem. The outside temperature sensor is connected to the programmer which does the calculation. The data is only displayed on the control head in the dash. Sounds like the programmer might be acting up or temperature sensor might be the problem. However the sensor (if bad) should set a code on the control head by a flashing LED. Then you have to retrieve the code.
I had similar problems and come up. I created a repair procedure of the programmer and wrote a thread on how to do it (I think it's a first on the Forum). The programmer lives above the gas pedal and is mounted on the firewall not easily seen. For the repair, some disassembly is required and knowing how to solder on a printed circuit board is more than a plus. Or you can buy one for several hundred dollars. I have repaired a couple so far.
The control head in the dash sometimes has dirty contacts and can be cleaned. The unit does have to come out of the car, disassembled and connector board pins and buttons cleaned. There are several threads on doing this procedure.
This is a common repair procedure.
There is also a possibility the programmer might be going bad. It can have different symptoms. No control over the buttons, LEDs not lit, stuck on a certain button and no temperature display but a back light.
What has got my attention is you temperature display problem. The outside temperature sensor is connected to the programmer which does the calculation. The data is only displayed on the control head in the dash. Sounds like the programmer might be acting up or temperature sensor might be the problem. However the sensor (if bad) should set a code on the control head by a flashing LED. Then you have to retrieve the code.
I had similar problems and come up. I created a repair procedure of the programmer and wrote a thread on how to do it (I think it's a first on the Forum). The programmer lives above the gas pedal and is mounted on the firewall not easily seen. For the repair, some disassembly is required and knowing how to solder on a printed circuit board is more than a plus. Or you can buy one for several hundred dollars. I have repaired a couple so far.
