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2000 Pontiac Gran Prix GT Air Conditioner Problem

My vehicle has a dual climate control system and the conditioned air that is emitted from the driver's vents is substantially warmer than that out of the passenger vents. This condition exists when both controls are set for the same temperature in dual mode as well as when set by the driver's control in non-dual mode. For instance left side air output is 72 degrees when the right side air output is 47 degrees.

The left side blend control motor and the exterior air temp sensor were both replaced with no apparent effect. The a/c technician working on my car said he got a 105 code when he ran the BCM diagnostics using the climate control system switches. He said the 105 code indicates a bad left side blend motor control motor and this code was present even after replacing the motor with a new one. He also said he was able to manually move the blend door from the full heat to the full cool when he had the motor out and could detect no binding during the full travel of the door. Unfortunately, he was not able to isolate the problem.

I suspect there is a wiring problem causing this situation but without a wiring diagram I don't know where to start. Any suggestions you have on isolating this problem will be greatly appreciated.

Ray

Reply to
Ray
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Here's what I have learned in the process of trying to isolate this problem:

  1. No OBD current codes are indicated when accessing the diagnostics through the climate control panel. A history code of 105 shows because I removed and replaced the driver-side blend door motor.
  2. With the driver-side blend door motor removed I could detect no binding when physically moving the blend door from full-heat to full-cold position. However, when the blend door was physically moved to the full cold position the temperature out of the driver-side vents was the same as out of the passenger side in single mode operation.
  3. Changing the driver-side temperature control from full heat to full cold positions appears to cause the driver-side blend door motor to move through its full travel (that is, from the full heat index marking on the motor to the full cold index marking). However, the driver-side outlet temperature is approximately 15 degrees warmer than the passenger outlet temperature when the temp control is in the max cold position.
  4. Replacing the driver-side blend door motor and the exterior temp sensor did not correct the problem.

It appears to me that for some reason the driver-side blend door is not being moved to the full cold position when the motor is installed and the temp control is set at max cold even though the motor appears to move to the full-close index mark. When I drive the motor to the full-cold position and remove it from the air box, the blend-door appears to be sitting in the full cold position.

Is it possible the a/c & heater controller is commanding the blend-door motor to a position just off the full cold position even though the motor appears to be at the index mark?

Because of item 2. above, I am convinced the blend-door motor is not moving the door to the full cold position even though the shaft position index on the motor appears to indicate otherwise.

Is it possible to adjust the blend door shaft positionslightly so the motor will definitely move the door to the full cold position when the temp control is set to max cold?

Ray

Reply to
Ray

Are you sure there's not something like a loose piece of insulation or paper or something blocking part of the AC evaporator core... so the driver's side just isn't getting all of the cold air it's supposed to? I had a foam "gasket" come loose in my Silverado's heat duct... and it made it's way into the squirrel-cage blower.

Reply to
David Courtney

The reason I don't think there is anything blocking a part of the evaporator core is that I can physically move the blend door to the full-cold air position and get 40 degree air out of the driver-side vents.

Ray

Reply to
Ray

Makes sense... I wish I knew more about how that system works.

Reply to
David Courtney

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