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squeaky AC problem related to bad air quality sensor

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my 04 CTT always makes squeaky noise from behind the PCM head unit. I dd some research and it might suggest a failing motor somewhere in the system. and I heard it is really hard to get to those motors so I kinda give up there.

however when I replaced the cabin filter last weekend under the glove box I noticed that there is a motor there connecting to a cup shaped valve behind the AC blower with a short plastic rod. and no matter I start the car with or without AC, the motor was always busy adjusting the "cup valve" with that short rod. that makes quite a bit of noise constantly since the motor is on and off on and off none stop.

now my question is: could a failed air quality sensor(I DO have a code regarding the bad air quality sensor) near the windsheld be the reason? my guessing is if the AC does not know the air quality/temp outside, it does not know how wide it should open the "cup valve" at the blower motor. so it constantly adjusts it.

any suggestions are appreciated. :)

oh the code is


air quality sensor

short to ground or positive

no signal/ communication


Edited by royxaxa
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If you unplug the air quality sensor(located near the brake master cylinder under the plastic cowl cover) and be sure the recirculating button is off and not on automatic then the door should stop cycling. If not then you need to reset the servo motor limits as the next step which requires the proper scan tool.

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  • 3 years later...

HI I'm hoping someone is still around on this post I have a 04ctt with an intermittent Ac problem works very cold after 45 min in the morning then leave it at work then works great from starting the car after being sat for 8plus hours any ideas sorry if I've double posted trying to get some help

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