caspermj

I've recently bought an 83 928S, US model. I'm trying to get the A/C working. When jumping across the relay, all fan speeds work but there is no control over the modes and it doesn't feel like the A/C is blowing cold, just outside air. Here's the "pickle" part: The controller has 1985 as a date on it (so it's not original). My car is serial number 861512. I know there is a change over in HVAC during this MY, do you think I could have a controller that requires the button on the central indicator panel to make the A/C work? I've searched lot's about this but am unsure of how to figure out which is correct for my car since I don't have the original to go by. Help!

caspermj

Oh dear! This really is a pickle! No one has any suggestions?

WallyP

Your problems are probably going to be difficult to solve, and will require diligent efforts on your part. It will be necessary for you to educate yourself on the HVAC system.

It would appear that you have two choices at this point:
- Buy, install and troubleshoot the correct control head for your system.
- Adapt the control head that you have.

It is not feasible to give you detailed instructions for troubleshooting and adapting until you have the wiring diagrams found in the Factory Workshop Manuals. Hard copies are expensive and difficult to find. The best approach would be to purchase a set of the 928 tech info CD's prepared by Jim Morehouse. Jim had every scrap of tech info that he could buy or borrow scanned, converted to pdf and burned to CD's. This is a huge amount of info, and includes the manuals. Jim's email is
jim928ATptd.net - change the AT to @.

You can go to our web site, then the tips section, then Wally's World, then the HVAC section and find a paper that describes the system and gives troubleshooting and repair info.

Let us know what your next step will be...

caspermj

Thank you Wally, I realize this will be a challenge. I might have opportunity to get a controller from a 1980 US, but I still don't know if it will be correct for my application. Is there a way to find out which is the proper one? Perhaps by looking at the wiring harness I have?

~Roy

WallyP

The '80 probably won't work - the early systems are quite different.

Jim's CD's include the HVAC training manual that covers the differences - that would be the easiest approach.

caspermj

Ok, I'll contact him an order a CD today. Thanks very much! I'll post once I receive it and am ready to tackle this

~Roy

caspermj

Just an update, still waiting to hear back from Jim, but I've heard back from the PO and he said the A/C never worked after switching the control unit. Even better, he thinks he has the original one around and will send it to me This could turn out to be a tasty pickle after all! At least with the proper unit I can trouble shoot more easily. FWIW, the PO has been extremely helpful before, during and after the purchase. He had the car over 14 years. More updates as they happen.....

~Roy





1983 928S US

Landseer

Roger at 928's RUS has been brokering the CD set, try him.

That's good news on the 83 controller.
Its the one with the double ECO modes on the front.
I had one, but gave it to GregBBRD.

WallyP

If you can get the original head unit, the problem might well be that the small relay inside the head has failed. There are several threads on here that give instructions on replacing the relay. Advanced search on HVAC and relay might show those.

caspermj

Landseer, Wally,

Cheers for the heads up. Fingers crossed he finds the old unit. I have read about the relay swap, would be nice if that was it. The PO said the A/C worked perfectly then just stopped one day. He swapped the unit out for the one in it now, didn't work so figured it wasn't the unit that was bad. The one he installed was a "known good" unit. The only problem was he never knew there was a difference between the two.

~Roy

caspermj

Landseer, forgot to say the pic in your avatar is one of my favorite 928 pics! Seriously, I love the wide angle "big shark nose" look to it