1993 HVAC controls

[Terry M.]

[Thomas W.]

Re: 1993 HVAC controls

Terry,
I haven't experienced this problem, but there is about 30 pages worth of information in the 1995 Service Manual on the Air Conditioning System and related controls. Lots of good information and diagnostic measures, particularly for the Electronic AC system - lots of sensors for temperature and various components that control how it operates. I think the 1993 system is the same. Might be worth it for your friend to get a hold of a set of 93 Service Manuals to work the through the various procedures. Too much to summarize here.

[Joe L.]

Re: 1993 HVAC controls

A note from a colleague with a 1993: “I cannot control the A/C or now the heat. It started this in late spring when I got in the car and as I was driving along, suddenly the A/C would turn on and off with no way of controlling it. The inside outside temperature did not display either. Every so often it would return to normal and I would be able to control the temp, speed, A/C, heat or defroster. Rarely but it did happen. Normally A/C would be on full blast and at a very low temp. It was like it was haunted. Most of the time it ran the A/C full blast. It got very uncomfortable in there.

I’ve replaced the dash controls to no avail. The people at Chevy also think it’s the programmer. I personally thought the programmer only open and closed the dampers for the system.”

Any of you C4 guys have any ideas for him?

Terry------


By "dash controls" does he mean the temperature control module in the dash (i.e. the unit with the buttons and temp display)? If so, did he replace it with a NEW/REBUILT unit or a USED unit?

As Tom described, he really needs to follow the diagnosis protocol in the service manual. There are numerous components in the system. Problem: many of the components are no longer available from GM.

[John G.]

Re: 1993 HVAC controls

Terry, the service manual is definitely the way to go, if it is electronic the display can show faults. When rebuilding my 93 there weren't any fault codes because the batt had been dead too long.....but I did find a vacuum line loose under the dash on the passenger side that cured my erratic hvac ops.
John G

[Terry M.]

[Joe L.]

Re: 1993 HVAC controls

I have to tell you I am not sure what he means by "dash controls." So far all of our communications have been by email since while I work with him we are at different locations and work for different companies. Corvettes have taken our conversations beyond business though.

I don't think he is up to troubleshooting or repairing this himself, but I will pass on your advice. The last message I had form him:

"The A/C Programmer was from Corvette Central and the dash controls were from and outfit in Florida . A bone yard. I also had a repair shop in Texas that fixed my stereo look at the original programmer and they claim it’s OK. They also repair programmers. That’s where I learned a programmer just controls the dampers. But the guys at Chevy insist it’s the programmer."

Terry-----


Sounds like the controller is used if it came from a Florida "boneyard". The problem with a used part like this is how do you know it's good? It might suffer from the same problems as the one being replaced. That can send one off on a "wild goose chase" if one assumes the used part is good and it's not.

These controllers are problematic.

[Terry M.]

Re: 1993 HVAC controls

Thanks guys, I will pass this on to him and see if we can make some progress over the winter.
Terry

[Richard M.]

Re: 1993 HVAC controls

I would refer him to Gordon Killebrew at 800-For Your VETTE nobody knows more about C4's.

[Terry M.]

Re: 1993 HVAC controls

I would refer him to Gordon Killebrew at 800-For Your VETTE nobody knows more about C4's.

Thanks Rich, I didn't think of Gordon. Good idea.

I had an email exchange with him this morning, and he does have the FSM. I may have to help him with that, but over the winter we will work on diagnosing this little better. Then if we run into a brick wall, I will have him call Gordon.

Thanks to all for your help.