Mystery X - Nobody Has A Solution?

[sjay]

I've taken my Berlina (2000) to TWO holden dealers and one independent mechanic and so far, nobody has been able to fix this. I'm posting this here in the hope that someone can point me in the right direction.

An X appears on the climate control screen. The error code is DTC 0021 Drivers Air Mix Door Error

The Climate Control Module (for aid con) has been replaced (twice).
The ABS Module has been replaced.

When the fault codes are erased, the aircon works fine for about a week, then the X comes back.

Occasionally I hear a clunk and it sounds like the door might be jamming. Would that necessarily cause the aircon to stop working? Is this a simple case of replacing the blend door?

[BlackVXGTS]

The info below may help. Replacing the air mix motor is a big job as the whole HVAC unit needs to come out.

DTC 21 - AIR MIX MOTOR DRIVERS SIDE (SZ/DZ)

CIRCUIT DESCRIPTION:
The air mix motor is actually an electric motor used to operate the air mixing door. The electric motor is sent a voltage signal of 12.5 volts from the ECC control module which causes the motor to turn, which moves the air mix door towards or away from the heater core, the direction change takes place by reversing the polarity of this motor. A potentiometer (PBR) is housed in the air mix motor circuit which feeds signals (3.6 ± 0.18 volts) back to the ECC control module as to the positioning of the motor and consequently the air mix door. DTC 21 will set: if the driver’s PBR feedback signal fails to reach the requested value. This will occur if the PBR or motor is open or short circuited, or if the air mix door is jammed or sticking.

An air mix motor or door problem will always be associated with non-regulated or incorrect temperatures from mode positions. The ECC control module, during calibration, sets a minimum and a maximum PBR value for the air mix motor in it’s memory. It is these values which determine the operating range of the air mix motor and against which all movements of the air mix adjustment are scaled. Any PBR signal value outside the minimum or maximum vale are considered a motor fault.
The ECC control module monitors the rate of change of PBR signal during air mix motor movement. If this rate of change falls to 0 (such as a broken air mix motor wire or physical jamb), the ECC control module will recognise the stoppage and set the fault code.
If DTC 21 was present before turning the ignition off, when the ignition is turned on again, the ECC control module will automatically try to re-calibrate the air mix door. This takes approximately 15 seconds. If the recalibration fails, then DTC 21 will be set again.

[TonyJZX]

i can't see this being under $1,000 just in labour

eww

[sjay]

So its pull the dash out and either:

1. Fix a broken air mix motor wire
2. Fix a physical jam

Is this a case of "its just better replacing the air mix motor" while you have the dash off?

[80shovelead]

have u tried checkin all the vacume hoses/lines on the back of the control unit?
had this happen in my calais and it was just a line that wasnt connected correctly

alot cheaper alternative than havin the whole dash out and bits replaced if not needed!