I bought a very used 90 coupe in August and one of the problems with it was that the AC/heater controls were inoperative and always in the heat mode (melting my shoes). Since winter is upon us I decided to tear into it. The problem turned out to be a bad programmer but I found that the previous owner had taken the dash panel off, disconected power to the electric door drive motor and manually moved the temperature door to the full heat position.

To make a long story short once I reconnected power to the electric motor the door moved to mid position and started oscillating back and forth over about 25% of the full range. This continued until I put the heater to the 90 deg setpoint whereupon the door moved to the full heat position. When I put the setpoint to 60 deg the door moved back to mid point and once again started oscillating back and forth. Doing the power reset procedure on the programmer does not seem to have any effect.

Looking the the position feedback signal I can see it fluctuating and it goes from +2 volts down to zero and then back up to a +1 volts. It seems to pass through the zero point on each swing.

This tells me that the position pot needs to be recalibrated .

My questions are:

1. Is there a easy way to adjust the calibration of the door drive
assembly without removing the drive motor ( seems like a real PITA)

2. Should the temp door move easily or is it stiff ? Mine can be moved easly but seems to have enough resistance to stay put.

Thanks.. and a Merry Christmas to everyone.

 

The only adjustment is the length of the arm. Since the Programmer is new, try disconnecting power - disconnect and reconnect the battery. Door should go through a recalibration - fully open to fully close and come to rest at whatever setting is shown on the Control Panel (usually 75) based on the signals from the inside and outside temp sensors. Don't touch anything while this is going on - maybe a couple of minutes - though usually the Controls are disabled until the Programmer learns the position of the door (which is what it's doing at startup once it's memory has been cleared).

 

Is this door operated by vacumn from the engine? When I start my car I hear a door that bangs open, or closed, whatever its trying to do. I know this is not right but don't know where to start looking.

Thanks

 

The temperature door is electrically operated. It takes around 5 seconds to move from one end to the other. If the noise is on the passenger side I'd take a look at the recirculator door. Its on the side panel directly above the passengers feet.

 

I had today off so I spent it trying to fix the temperature door. This is frustrating.. Everything checks out but the temp door still wags back and forth. Doing the reset procedure does not seem to affect anything.

Does anyone know whether the AC Programmers are interchangable between 90-95 ? Thats what it boiling down to.. The programmer I installed was used and I was told it was from a 92. All of its functions work fine with the exception of the temp door.



Time to take break and have some leftover pie.

Cheers.

 

Always the possibility that it's the Control Panel - Dialed in Temp comes in over the Data Line and then the Programmer does it thing. You'll need a bi-directional scanner to bypass the controls. If that moves the door and it stays put, you need new Dash Controls (actually, I think only reman is available). Programmer appears to be interchangeable - x-reference at www.acdelco.com shows a Part # of 15-71773 - used on '90 through '96 Vettes only (surprised me because I thought it was used across the line). I'm off for some leftover Ham and Roast Beef -