Has anybody ever replaced the HVAC Programmer?

[QB93Z]

I have been trouble-shooting an HVAC problem on my Yellow 1994 ZR-1 for a while now. I replaced the Heater Door Control Motor and it fixed on problem, no heat in any mode.

But I still have a problem that in normal operation, all of the air flow comes out the windshield defroster grill instead of the passenger grills on the dash.

After all the trouble shooting in the manual I got to the step to replace the HVAC Programmer. The Programmer is a small box that distributes a vacuum source to 4 pneumatically operated flappers.

The problem is that I can't get the Programmer out. It is located about 14 inches above the gas pedal. There is a lot of wiring and other parts and pieces in the way of removing it. It has an electrical connector and a manifold with 5 vacuum lines.

Has anyone ever worked on this?

Jim

[secondchance]

http://www.c4vetteregistry.com/vrfor...rostor/428975/

http://www.corvetteforum.com/forums/...airs-them.html

Similar issue discussed.

Do you have a spare programmer or going to remove, disassemble and see if can be repaired?

[QB93Z]

I have a spare. I just bought it from Dempsey on Thursday so that I could take this on.

I also have all the moving parts of the HVAC system including the "tubing harness" I just haven't been able to get the programmer out. I may have to cut off the hoses and try that. I will have to run one tube to the passenger side of the dash.

Jim

[WVZR-1]

Isn't it just remove electrical connector, the vacuum harness, the lower mounting bolt and drop out of the retaining tabs?

What year programmer did you buy? I thought '94 and '95 were the same but I would have thought different from earlier.

'94 programmer mount.jpg

[S.hafsmo]

The electrical harness is long enough to drop to the floor before removing. Most wires can be moved aside with cable ties. Biggest problem is this one way washer/clip that is pressed on, holding the vacuum connection in the center of all the hoses.

I took the seat out and the metal knee plate to gain proper access, and a small flat screwdriver to pry up one side of this washer, then managed to get a needle nose plier to bite over it and pulled straight out. Probably used an hour on that little bastard.

Once it's of, the rubber connector prys off, and programmer can be dropped.

[QB93Z]

Yes, the first step seems to be getting that "pressed on" nut off so the vacuum line connector can be removed. Then maybe I can turn it to a more advantageous position.

You are correct, removal of the seat was step 1. Along the way, I had to remove the dash pad to get access to the Defrost/AC damper that is not moving to verify that it was not stuck or had a failed linkage. Even with the dash pad removed, it is difficult to work on the actuator because it is very close to the windshield.

I will try again tomorrow. Wish me luck.

jim

[-=Jeff=-]

Originally Posted by QB93Z

Yes, the first step seems to be getting that "pressed on" nut off so the vacuum line connector can be removed. Then maybe I can turn it to a more advantageous position.

You are correct, removal of the seat was step 1. Along the way, I had to remove the dash pad to get access to the Defrost/AC damper that is not moving to verify that it was not stuck or had a failed linkage. Even with the dash pad removed, it is difficult to work on the actuator because it is very close to the windshield.

I will try again tomorrow. Wish me luck.

jim

That pressed nut is a PITA, I would rather swap a heater core than remove that one nut..

I have pulled them off before it is difficult and in a not so easy place to get at

[QB93Z]

Originally Posted by WVZR-1

Isn't it just remove electrical connector, the vacuum harness, the lower mounting bolt and drop out of the retaining tabs?

What year programmer did you buy? I thought '94 and '95 were the same but I would have thought different from earlier.

Attachment 5998

I am working on a '94. My spare is from a '91. The shape and external features of the boxes appears the same, at least the best I can tell with the installed box still under the dash.
From the other sites and threads I have reviewed, the problem seems to be collapsing of the rubber block multiple tubing fitting. The spare tubing set I have is identical to the '94. I was hoping I could get the Programmer box out from under the dash but still connected electrically and then test the functions with a vacuum gauge.

[S.hafsmo]

Haibeck seemingly had no success using a programmer from an earlier Z on a 94, as he mentiones here.

Originally Posted by Haibeck

BTW, the earlier Programmers will not work on a '94. I had to find a '94 Programmer to fix the '94.

[QB93Z]

Progress!! The problem with the air flow controls is now working correctly. I never did get the HVAC Programmer out, but I was able to apply a vacuum source to each controller and they all worked. Then I determined that the vacuum tubing between the plenum and the Programmer may have been kinked behind the Passenger side hush panel.

Now I need to get the "Air Mix Door" synced so that it stops giving heat when AC is requested.

BTW, I have never gotten any trouble codes on the Control unit.

Jim