A/C and Heating - Climate Control Issues



Back again folks!

I recently (about 6 weeks ago) replaced the HVAC programmer module in my 1990 Buick Riviera. One night, two of my pals and I were cruising around Port Orange, FL, just enjoying talking and driving. As we drove on, I noticed that the car was getting a little warm (this car has fully automatic climate control, so it’s odd for it to deviate from the set temperature, especially when there’s no sun out to randomly peer out from behind the clouds and warm the car). I turned the climate control all the way down to 60? (Max Cool). The A/C was running. But it got warmer and warmer. Eventually the air coming from the vents was so hot that I had to shut the climate control off and open the windows. But even with the fan off, the air coming in the vents still blew out hot, as if the mix door was open. The car became unlivable and we had to go home.

It turned out to be a faulty programmer module at fault, hence why I replaced it. I checked the air mix door before installing the new (well, actually used, module), the rod moves freely and there’s no binding of any kind.

When I installed the module, I found that it leaked vacuum and the vents did not work correctly. So instead of installing the new module, I removed the air door actuator motor and sensor assembly from the module. Thankfully it used a 4pin connector to connect to the circuit board, no soldering required. I swapped this into the old HVAC module, and installed the old module. I watched as the newly assembled module pushed the blend door all the way from open to closed. (I should have checked the Body Computer data to be sure it hit both stops but I didn’t). Both heat and A/C came from the vents now, and the car could always maintain my prefered 73??F.

Now it’s not working again.

I’d hate to think I have to replace this module again seeing as I paid 75 dollars for the first one. No one makes these anymore as I know of it (and if you happen to know someone who does or has one PLEASE let me know). So they’re not cheap and have to be obtained by salvage.

Although I have not physically tested the module yet I have fairly convincing evidence that the module is at fault. Using the OBD system I was able to monitor the actual reported sensor value for the door’s position (0 being closed, 99 full open/full heat) while manually overriding the BCM’s commanded value. The door’s position never got below 21, and never managed to get above 56. And it only seemed to react once I set the value close to its limits, never when I changed in moderation and within the 21-56 range.

So I’m wondering what could cause this to fail again. Because if there’s anything worse than having to do a repair twice… it’s having to do it once more again.