[ChevyTech]

These door motors have a position sensor circuit in them. If this position portion of the motor fails the controller (in the AC head) will not know the correct position of the door, and could run it into the end of travel and then make the gears jump as it runs after it should have stopped. The system has a fail safe design that shuts the motor off after it sits and slips a while.


The recirc door motor can be changed without removing the airbox, but it is not easy.
Here is how I do the job:
I pull the carpet and carpet pad away from the firewall and fold it back by the seat to give a little better access.
I use a ¼ inch drive air ratchet to remove the screws that attach the motor to the airbox.
I pull the motor down and then unplug it.
Plug in the new motor.
Put the screws in their holes and poke each of the screws through a piece of plastic to hold them in the motor. The plastic can not be so strong, or think, that it causes a problem, but must be substantial enough to hold the screws from falling out.
You may need to run the motor if it is not in the correct position to install it.
Get the motor in place and tighten each of the screws partially so you don’t make a screw fall out as it get pushed by the motor moving to a fully seated position.
Once all screws are started, then you should tighten all the screws.

The only way I can do this is with my small 1/4" air ratchet. There is not enough room to swing a regular ratchet in that small area.
Care must be used to run the ratchet very slow and not over tighten the screws.