Computer and A/C
Thread Starter
Instructor
Joined: Sep 2004
Posts: 177
Likes: 2
From: Palmyra Virginia
Computer and A/C
I hope I'm posting this the right forum, if not please excuse me. I have a 92 coupe that has never blown cold air through the a/c I took in yesterday for trobleshooting and repair, mechanic sys they found a couple of burnt wires which they repaired and topped of the freon as it was very low. He says it appears the computer has been reprogrammed (there is sticker of some kind that indicates this) and that I need to hace the dealer reprogram the computer and that should solve the a/c problem. He says everything else checks out ok but no signal from computer to compressor? Is this a reasonable diagnoses? And if so what kind of codes should I get when scanning? Thanks in advance.
Advanced
Joined: Sep 2005
Posts: 64
Likes: 1
From: Columbus Ohio
You may want to repost this in the C4 Tech/Performance section. It has a wider audience.
If the 92 is similar to my 90 then there is a signal from the AC programmer to the Engine computer (ECM) that tells the ECM to engage the AC compressor. It does not seem likely but its possible that if your ECM was altered that function was lost. A more likely senario is that you have a defective programmer, AC relay, pressure switches and/or compressor clutch.
This is where having the factory service manual is a great help. It gives a step by step troubleshooting procedure to quickly isolate the problem.
Are the other HVAC functions working normally?
If the 92 is similar to my 90 then there is a signal from the AC programmer to the Engine computer (ECM) that tells the ECM to engage the AC compressor. It does not seem likely but its possible that if your ECM was altered that function was lost. A more likely senario is that you have a defective programmer, AC relay, pressure switches and/or compressor clutch.
This is where having the factory service manual is a great help. It gives a step by step troubleshooting procedure to quickly isolate the problem.
Are the other HVAC functions working normally?
Advanced
Joined: Sep 2005
Posts: 64
Likes: 1
From: Columbus Ohio
My suggestion is to get the service manual and run through the HVAC troubleshooting procedures.
Another approach ( assuming its the same as a 90) would be to bypass the AC relay. Its the dividing line between the digital electronics and the compressor subsystem. If the compressor engages then you know the problem is in the digital side. Conversly if nothing happens then focus upon the pressure switches and clutch. The AC relay is located to the left of the steering column facing backwards. You need to remove the trim and the aluminum knee bolster.
I still recommend the getting the manual and reposting in the other section. A lot more people will see it.
Another approach ( assuming its the same as a 90) would be to bypass the AC relay. Its the dividing line between the digital electronics and the compressor subsystem. If the compressor engages then you know the problem is in the digital side. Conversly if nothing happens then focus upon the pressure switches and clutch. The AC relay is located to the left of the steering column facing backwards. You need to remove the trim and the aluminum knee bolster.
I still recommend the getting the manual and reposting in the other section. A lot more people will see it.
Burning Brakes
Joined: Dec 2000
Posts: 1,161
Likes: 0
From: Orangeburg, NY
I saw this advise on another post but don't know if it actually works. The post recommends to pull the Radio and interior light fuses and keep them out for about one minute. The post says that this resets the a/c programming to "original specs." It's worth a try, nothing to lose.
