Regardless of the setting on the climate control, the air only blows on the windshield. Anyone run into this before?

 

It was one quirk of the 1996 MY. The little rubber-like nipples on the back of the controller collapse and choke off the controlling vacuum. A little bit of surgery will restore its functionality. I'll try to find the writeup with pics and post a link here for you.


OR


The vacuum line from the engine compartment is open or broken. Does your cruise control still function?

 

if you find you need a new HVAC programmer, I have a good used 96 version.

 

First, inspect the vacuum check valve under the passenger side fuel rail cover - it your cruise control is also flaky, this could be the culprit.



Otherwise, here's a good thread:
http://forums.corvetteforum.com/c4-t...l-problem.html

 

Thanks guys. The cruise is working, but I'll check those out anyway. Any links would be appreciated. I'll keep you in mind VetteMed if I need one.

Good link pianoguy. Sounds like the same problem I'm having. Does anyone have a picture or link to a picture of the programmer/manifold? I'm gonna have to get someone smaller (and younger) than me to remove the unit.

 

The link pianoguy posted used to display pictures that showed the issue very clearly.
It seems the site where the pictures were hosted is no longer available though.
Post #13 from Digital Disaster had pictures. links are still there, but nothing ever shows up.

I saved that link a long time ago (for when I might need it in the future).
I wish I would have saved the pictures too now.

 

I have not had the C4 programmer apart, but on other GM AC programmers a common failure is at the vacuum connection. It sounds like the 96 programmer is similar.

There is a cone shaped rubber connector with a hole for the vacuum path that is captured between two plastic sections. There is a rubber cone for each vacuum line. On my mom's there were 5 or 6 of them. When the connection is made and the two plastic block sections are squeezed together they compress the rubber cones and make the vacuum seals. This works fine, but as the rubber ages they don't have the strength anymore and when there is a vacuum source the rubber cones collapse and seal themselves off. When this happens the programmer can not change the airflow between the vents, heater, and defroster. On my mom's car it left the defroster and heater vents on but could not shift to the dash vents.

The AC programmers are expensive. If the rubber cones collapsing is the problem, I have fixed a few without removal of the programmer. You can split the two plastic connector block sections to expose the rubber cones. I took some hypodermic needles (I think they were the pink colored ones from Walgreens) cut them to the right length and blunt both ends. Insert them into the vacuum openings in the rubber cones to keep them from collapsing. The hypodermic needle provides the vacuum air flow path. The air flow path needs very little opening and is a very low flow, so the hypodermic needle has enough flow. Reconnect the plastic block sections trapping the needles in place.

On my mom's car, for the AC programmer to be installed by the dealer it was going to be about $1000 with about half being the part. I fixed it by the method I described above. Total cost was about 25 cents and it only took about an hour. Most of that was cutting the needles and making sure they were not sharp. The repair was done about 8 years ago and is still working fine.

If this is your problem, I hope this helps.

Good luck.

 

Here's an article with some pics:

http://www.imcool.com/articles/airco...acuum_line.php

I used a male connector from a '95 programmer, but any of the other fixes mentioned should work fine. But it does take some patience to do the job, and being a midget contortionist would help a lot ;-)