My climate control has been acting up for years and I am sick of it, but not sure what to replace. Please tell me what is the most likely source of the problem. These are the symptoms and some things I have checked:

- fan doesn't always work
- fan sometimes blows only through defrost and lower vents
- fan sometimes blows through correct vents
- fan sometimes comes on when going over a bump
- climate control sometimes swithces to the auto mode when I start the car, no often though
- I have had the "check valve" under the valve cover cleaned and checked
- had the T-fitting checked
- I took out the head unit and cleaned contacts, and banged on it to see if it would start fan- no success
- tried to remove under dash controler box, couldn't get it out, banged on it and fan didn't start

So what do I need to replace, the fan, head unit, or controller under the dash?

The problem is so speratic and hard to pinpoint, plus it has symptoms of all 3 things. I can't tell if it's a bad connection or bad vacuum. :mad

 

95wht6spd

I have similar symptons to you but not as bad.

Please let me know how this turns out.

rwaibel@direcway.com

BTW
I have a 95 BLK/BLK AUTO

 

A tee connector and a vacuum gauge will tell you if your vacuum is intermittent. The electrical repair manual only says to replace the heater and a/c control assembly for intermittents, but then this manual was meant for GM service people who are not expected to service down to the component level on circuit boards. I am having minor intermittent problems too, but haven't gotten into the contoller yet. The controller has a microprocessor in it , so if it is defective , it is not available and replacement of the entire controller is required.

 

This sure sounds like flaky power connection to the controller chip. Mine will go to auto if the battery has been disconnected. Check the connections to the controller unit that you use to control the HVAC system in the dash

I know these units have problems with the solder connections on the circuit card after miles of bumps. I had one replaced under warranty because the main led was flaky. The replacement one finally developed the same problem. I reheated the solder joints on the leds and the problem has gone away. The button contacts get dirty also and need cleaning after a few years.

If you are not familier with soldering, get a replacement unit. The replacement one in my car was a refurbished part despite the fact that it was replaced by GM under warranty. That means the factory must replace a lot of these units under warranty.

 

I took the head unit out and cleaned the contacts and beat on it while it was connected, but the fan never came on. Couldn't it be a bad fan, maybe the brushes have worn down, may be it is also the head unit? I just don't know, I realy don't want to replace all of them.

 

Don't know what to say, but I'll say what fixed mine 100% . I had same problems as you....although I had problems where you'd push a button and nothing would happen (until you banged on the dash a couple times).

I took my climate control unit out (the thing above the radio). Opened up the plastic box its in, pulled out the circuit boards, pulled off the connectors, including the face display unit from the main circuit board, put all the connectors back on, pushed the face display back onto its connector on the main circuit board, and have had no problems ever since. Works great every time.....didn't have to clean any contacts or anything. A connection must have been loose and my guess it was where the face unit (With the display and controls) plugs into the main circuit board.

I am assuming your problem is similar. If its not. good luck and keep us posted.

 

Check this out go to the Climate control section. http://www.batee.com/corvette/

 

I am ordering the fan (blower) today, it is the least expensive part. Hopefully this will fix the problem if not I will try the programmer and then the head unit. I will keep everyone posted.

 

There is a way to diagnose problems in the C68 climate control system. But, unfortunately it requires a Vetronix Tech-1A, MasterTech, or the Tech-2 with a cartridge for the "body" computers. Most GM dealers have these scan-tools.

As described in the '92 Corvette shop manual, you have to temporarily connect the climate control serial-bus (this is a serial-bus that connects the C68 Control head to the Programmer) to the E&C serial bus (this serial-bus is how the radio control head communicates with the radio receiver (above the glove box) to be able to use the scan-tool on the C68 Climate control.

Once this is done, you can use the Tech-1A to monitor all communications between the C68 Control head and the programmer. If you believe the problem is the Control Head, you can use the Tech-1A to send the correct commands to the Programmer to see if it responds correctly. After you are done, you have to disconnect the temporary connection between the two serial-buses. I connected the two buses with a switch, so I can diagnose mine, in a matter of a few minutes, by just throwing the switch and connecting up the scan-tool.

However, I bought a Tech-1A, with all the cartridges for all the computers on my '92, several years ago. It is one of the best investments I have made -- so, far it has diagnosed my intermittent Opti-Spark problem, my ECM problem, my ABS/ASR problem, and my C68 climate control problem. Plus, I can take a snapshot of , up to, 60 frames of engine, or any computer, data then download the snapshot to my PC to graphically analyze the different data sets by comparing parameters. One good example: when I had an intermittent engine misfire that set no codes, I hooked up my Tech-1A and manually triggered the snapshot when the misfire happened. By graphing the results on my personal computer, I could compare the knock sensor output with the throttle position to determine that I had intermittent extremely high level knock retard at a throttle position that was only 10%. This told me that there was extreme premature ignition when just cruising, which led me to believe that the Opti-Spark was the problem. After taking the Opti-Spark out, I found it was carbon tracked allowing the next cylinder in the firing sequence to fire 90 degrees early.

Tom Piper

 

Sounds good....what time can you stop by? ;)