Any ideas?

It's the 3 dial system from a 2000 1500 reg. cab. I tried hooking up the same style head control unit from my '02 Tahoe with no results (same part numbers, so they should be compatible).

Air only comes from mid level vents. No defrost, feet, or combination. A/C is functioning and unit does swtch to/from recirculate/outside as well. Just does not like any other position....

Just a hunch- look above the gas pedal- is the arm to the diverter door still connected- I have found two or three lately that were not connected....the door will flop into its most convenient position.....

I'll check. Thanks.

If you can't find the arm that brcidd described, look for this.

I'm pretty sure on your 2000 that the mode/diverter door is controlled by a small motor. The motor gets its signal electrically from the switch panel dial position.

This motor is located on the left side of the plenum right above the tranny hump. Look for 3 wires: White, Brown & Black. Pull the motor and see if it moves with the switch dial. Be sure the key is in the run position and the fan switch is in any position except off.

If you can't find the arm that brcidd described, look for this.

I'm pretty sure on your 2000 that the mode/diverter door is controlled by a small motor. The motor gets its signal electrically from the switch panel dial position.

This motor is located on the left side of the plenum right above the tranny hump. Look for 3 wires: White, Brown & Black. Pull the motor and see if it moves with the switch dial. Be sure the key is in the run position and the fan switch is in any position except off.


this is correct it is called the mode door actuator, it is usually a bad mode actuator motor, or the door is sticking ice,debris,,,,as stickman said remove from air box and if it don't move and there is voltage to motor thats it.....

this is a 5volt dc motor! not 12volts