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/vrforums/c4-cooling-and-heating-systems/air-only-comming-out-of-the-windshild-defrostor/428975/

http://www.corvetteforum.com/forums/c4-tech-performance/3035297-ac-programmer-is-bad-i-need-to-know-who-rebuilds-or-repairs-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.

5998

[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=-]

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]

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.

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 (http://www.zr1.net/forum/showpost.php?p=257603&postcount=18).

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

[secondchance]

Great to hear you have zeroed in where the issue was.

[dredgeguy]

Progress is a good thing! Let me know if you need another pair of hands.

[Roadster]

Then I determined that the vacuum tubing between the plenum and the Programmer may have been kinked behind the Passenger side hush panel.

Jim, you lucked out on that one, no need to remove the HVAC programmer is a big plus!!!

[QB93Z]

I received the Heat Blend Door Motor that was supposed to be for '93-'95 that I bought on eBay. I installed it in the car with confidence that everything would work properly.

Well, I have the same symptoms that I had with the Heat Blend Door Motor from the 1991. When the controls are set at 90 degrees, (calling for heat), it blows cold air out the lower vents. When the controls are set at 60 degrees, (calling for AC), it blows hot air out the AC vents on the dash.

I suspect that the motor that the eBay dealer sent me is not really the late model version.

Pictures to follow.

Jim

[QB93Z]

In this pic, top is the controller from my 1994. The corrosion from the AC condensation has damaged the small motor. Below it is the motor from the 1991.

https://uploads.tapatalk-cdn.com/20170310/33257f3d95fbfa44764de297983e7af8.jpg

There is a difference between them. The wiring to the motor is reversed:


https://uploads.tapatalk-cdn.com/20170310/a0d7715c7831fba7da380e8ba15852bd.jpg

https://uploads.tapatalk-cdn.com/20170310/a68228cb9fb2e43b284a52942f5ab5f2.jpg

I swapped the motor leads to reverse the direction and tried it in the car again. The blend motor appeared to run in the correct direction, but it only moved a small amount then stopped. I believe that the unit has a position signal that goes to the HVAC Programmer. So that signal has to be reversed as well.

Jim




Sent from my iPhone using ZR-1 Net Registry (http://r.tapatalk.com/byo?rid=90383)

[QB93Z]

Both the 1994 and the 1991 unit have the same GM part number: 16124952

Does anyone know how to identify the correct version in the parts sources?

Jim


Sent from my iPhone using ZR-1 Net Registry (http://r.tapatalk.com/byo?rid=90383)

[-=Jeff=-]

did you disconnect the battery before putting that assembly back in? if not do that for a minimum of 30 seconds.. then try again. Blend door will calibrate and then you can control it

[QB93Z]

did you disconnect the battery before putting that assembly back in? if not do that for a minimum of 30 seconds.. then try again. Blend door will calibrate and then you can control it

You are correct, and I forgot to do that the last few times I put the unit in. I will try it.

Thanks, Jim

[S.hafsmo]

Did the 30 sec recal. help?

[QB93Z]

Did the 30 sec recal. help?

No, I still had the same symptoms. I have been retracing all my steps in this drawn out trouble shooting process. Now I am wondering if the wiring harness from the main harness to the Heat Blend Door Motor makes a difference. It occurred to me that I have been using the harness from the 1991. I have gotten busy with other projects and haven't had a chance to test that theory yet.

Jim

[S.hafsmo]

Strange. Did you try asking WVZR-1 to check differences between the pin-outs for those model years?

[QB93Z]

In the FSM, under the Symptom: HVAC Programmer is not functional, there is a diagnostic procedure to measure voltage on most of the connections between the Programmer and the connectors and to the Door Motor. Unfortunately I have not been able to get the Programmer out to where I can remove the connecter or get a probe to accurately back-probe the wires.

If my harness change does not solve the problem, I will have to begin disassembly of the components in the driver's side foot well so I can access the Programmer.

Jim

[S.hafsmo]

Is it a 94 FSM you're using? If so, I can post the connector pin-outs from my 90 FSM (think they're the same as 91) if you'd like to compare them. Should give you a good hint to whether or not the harness is the same.

Sent from my SM-T719 using ZR-1 Net Registry mobile app (http://r.tapatalk.com/byo?rid=90383)

[Roadster]

Jim, did some research....maybe you have already seen this, from CAC in 2006.

"HVAC Programmer/Temp Door Fixed!

Well, I am pleased to report that the temperature door on my '89 Ebay rat is now fixed after much study and many questions (it wasn't working when I got the car, notwithstanding the claims of the electrical engineer who said it was fixed by him----go figure). The problem was that, as I suspected, the HVAC programmer was bad. I replaced the programmer with a new one from gmpartsdirect.com this weekend, and gritted my teeth as I switched the controller from full air conditioning to full heat. Voila! It was one those triumphal moments that I am sure you can all appreciate. So, the lesson is this: If everything works on the electronic HVAC system except that the temperature door does not swing from full by-pass of the heater core to flow through the heater core, then the problem is probably the HVAC programmer. From some tests I ran it also appears that the temperature door does an automatic default to full by-pass of the heater core if the programmer is defective. Here in Houston, it was 80 degrees yesterday, so the rat and I went down to Galveston to go surfing and we ran into a dense fog bank (virtually no surf and no visibility cancelled surf plans). The outside temperature dropped about 15 or more degrees within three miles from the beach, so I got a chance to try out the heater for real. It seems to work great!

/s/ Chris Kennedy
Houston, Texas"

Also a link for a remanufactured HVAC Programmer if you do in fact need one....
https://corvetteparts.com/item/programmer-heater-air-conditioning-controller-c68-electronic-option-1994-1995

[Roadster]

Some other links.....

http://www.ebay.com/itm/AC-HEATER-PROGRAMMER-C68-C4-Corvette-1994-95-NEW-NOS-/331920714752?fits=Model%3ACorvette

http://www.ebay.com/itm/1994-1995-C4-Digital-A-C-Controller-Programmer-USED-Corvette-/291999516723?fits=Model%3ACorvette


Also a video on rebuilding the complete system....the head unit, the blend door and the HVAC programmer.

https://www.bing.com/videos/search?q=1994+Corvette+HVAC+Programmer&view=detail&mid=2ADF880C19F1D98E47EE2ADF880C19F1D98E47EE&FORM=VIRE

And blend door repair kit for the gear, couldn't find anything on the motors....

http://blenddoor.com/product/gm-blend-door-actuator-rebuild-kit/

[QB93Z]

I believe that I have solved all the problems with the HVAC system. This afternoon I got cool air from the dash vents when it should, warm air from the floor vents when heat was needed, and air blowing on the windshield only when it was supposed to.

As a summary, the problems that I corrected were:

1. A pinched vacuum line to the HVAC Programmer Module. This caused sluggish or no operation of the vent system dampers so the air would blow in the wrong places. Repaired by adding an elbow and rerouting the tubing.

2. Damaged electrical connector at the vent blower control resistor. This caused intermittent operation of the vent blower. I replaced the connector.

3. A failed Blend Air Door Motor. This caused the HVAC system to never add warm air when heat was required. I replaced the motor.

I did solve why I had the problems with the Blend Air Door Motor. During my trouble shooting of the failed motor, I tried to install the motor from a 1991 system. I deduced that the motor had to turn in the opposite direction than in a 1991 system because the location of the motor was changed in 1994 and after from the top of the duct to the bottom of the duct. I tried swapping the +DC and -DC wires in the wiring harness to the motor. The 1991 motor did not work at all with that wiring. I bought a 1994 motor and installed it. Since the 1994 wiring pigtail had the swapped wires. I used the 1991 harness pigtail. --- Big Mistake-- Every motor I tried operated, but in the opposite direction to what was required. It took me a week and a lot of research to figure out that I had introduced the problem since the 1991 harness pigtail was wired differently from the 1994 pigtail. Today, I restored the + and - wires in the 1994 pigtail, and the system works with the 1994 motor.

http://i407.photobucket.com/albums/pp152/QB93Z/Misc/255003AA-3C58-4485-A1CE-2483526B83A1.jpg (http://s407.photobucket.com/user/QB93Z/media/Misc/255003AA-3C58-4485-A1CE-2483526B83A1.jpg.html)

Adding to the confusion of the motors is that the 1991 and the 1994 motors have the same GM Part number (16124952), and look the same, but they are wired differently internally.

It has been an excellent learning experience and now I can reassemble the interior and move on to the next project.

Jim

[S.hafsmo]

Well done, Sir.
Appreciate you taking the time to sum it up for the rest of us.

Sent from my SM-T719 using ZR-1 Net Registry mobile app (http://r.tapatalk.com/byo?rid=90383)

[secondchance]

I am a bit confused. Why did you try to use 91 harness?
Nonetheless, great to know that we have HVAC specialist within the WAZOO.
Great job!:cheers:

[secondchance]

Jim,

One question - any idea what caused moisture build up around the motor? Poor design? Any way to avoid motor corrosion? Do you see motor corrosion as being unavoidable for later Zs with AC operation?

[QB93Z]

I used the 1991 harness when I got the 1994 motor from eBay. I didn't give a thought to possibility that it might be different. To me at the time, it was just a connection to the harness from the Programmer. Two demerits for sloppy trouble shooting.

Regarding the corrosion in the old motor. The water must come from the condensation in the AC evaporator. The condensation must collect in the duct and then overflow the opening for the blend door shaft, into the motor. I plan to figure out where the evap drain line is and make sure it is not plugged. The motor is not watertight at all. Water leaking around the operating shaft would drip onto the passenger hush panel and then onto the passenger carpet just like a heater core leak. Now that I think about it, the moisture in the motor could be coolant from the heater core. But I have never had evidence of a heater core leak.

More things to investigate...

Jim

[dredgeguy]

Well done Jim!