'97 Park Avenue - passenger heat goes cold then hot then cold, etc.

My son's '97 Park Avenue started making a strange groaning sound under the dash and the passenger heat alternates between hot and cold. No matter what position the passenger sets his control to, it goes from full heat to full cold and back and forth. It sounds like a door is constantly opening and closing.

We disconnected the connector at the HVAC controller that controls the actuators, leaving the second connector plugged in. He can now control the fan so he has heat, but of course there is no airflow control at all.

Has anyone had a similar problem?

Read this link. http://www.automotiveforums.com/vbulletin/showthread.php?t=883854

it might help:runaround:

Read this link. http://www.automotiveforums.com/vbulletin/showthread.php?t=883854

it might help:runaround:

Thank you. I did read that and some symptoms seem similar, but I didn't see a solution. I'll ask my son to read this and get his comments.

Mine did the same thing and it was the control head.
eBay 45.00-85.00
Dealer is 300.00 plus

Mine did the same thing and it was the control head.
eBay 45.00-85.00
Dealer is 300.00 plus
Thank you. When you say "control head", do you mean the HVAC controller, i.e. the computer behind the glove box?

While working on the engine, we had the battery disconnected for a few hours. Then this started happening when we reconnected the battery.

There are two connectors into the HVAC controller - one controls the actuators, which he currently has unplugged so prevent them from operating. Otherwise, the door keeps opening and closing, letting the passenger air change from full warm to full cold.

Do you have a part number, by any chance?

Sorry,mine was the Heater A/C Climate Control Unit.I noticed the luminated area would go dim.I don't think that's your problem but,I could be wrong.
I read on here about resetting something to fix that.Now I cannot find it.

Sorry,mine was the Heater A/C Climate Control Unit.I noticed the luminated area would go dim.I don't think that's your problem but,I could be wrong.
I read on here about resetting something to fix that.Now I cannot find it.

Without the Service Manual in front of me, I don't remember the exact name of the controller, but it could have been the Heater A/C Climate Control Unit. Was it located behind the glove box?

I'm speaking of the actual controls.The buttons you push to control the A/C and Heat.

The "A/C climate control (head) unit is located in the dash, the one with digital display. The "Programmer" is located behind the glove box. This is what controls all the blend doors. If you have a flashing light (at start-up) on the control unit in the dash, this is telling you that there is a fault in the system. The dealer can scan this system with a Tech II and tell where the faults are. They can also recalibrate and clear codes. Did anyone remove the battery terminals while the A/C controller was still on?

My son and I were working on the engine intake manifold and a coolant leak, and prior to this work we disconnected the battery - while the ignition was off of course. The battery was disconnected for a few hours, because we also had the instrument cluster out while replacing the fuel sender unit - we were doing a number of projects, but nothing obviously related to the HVAC system.

When the work was completed and we reconnected the battery and turned on the ignition, the "groaning" started, and it sounded like one of the air doors was moving from open to closed. The passenger temperature could change from warm to cold, no matter what the passenger temperature was set at.

My son advises there are no indications of any faults or flashing indicators. He borrowed a "scan tool" from a local auto parts store and found no codes at all, however, we are told that the inexpensive engine scanners may not show body codes, which perhaps the HVAC system would set.

If members of the forum cannot offer suggestions, the next step will be to have someone with a complete diagnostic scanner see if he can pull any trouble codes.

Currently my son has the second connector on the "programmer", if that is what it is called, pulled to prevent the door from continuing to open and close. With the primary connector still connected, he has only fan control, but no actuator control.