Last year I rebuilt my HVAC system on my 88 truck. It has the old control unit WITHOUT a MAX AC button. Local shop sold me a Dorman actuator that worked for a few months. I got it to work by grounding the second wire coming out of the high pressure sensor on the back of the compressor. Then it stopped. Now, after some research w Dorman, they stated they do not manufacture a fresh air inlet (recirculate) door actuator for that vintage. Why this one worked for awhile, who knows. Called GM, they said they could not find one anywhere in the country for that era truck. Before I play hit or miss, can anyone give me some direction as to where I can obtain one of these?
I rummaged through the old actuators and MAY have the original recirc (it didn't work for a long time, but may have been due to not getting a signal). IF the actuator I have in hand is the air inlet unit, it has six pins and spins freely when the first two are connected to a 9V battery. From what I understand, the original actuator only has two or three pins, so maybe the ones I have in hand are the wrong type. My assumption is that it goes into recirc when it senses high pressure off the compressor in that it would open to fresh air once the AC was set to low fan or not to coldest setting.
For now, the system is charged and blowing cool, with the recirc door locked in recirc mode with bailing wire to hold back the Texas summer heat, but it would be nice to have the old truck working properly.
Thanks for your time and interest.
If all else fails, I may rig up a cable to manually change it to fresh air as needed.