Question about 1991 GMC Sierra
The owners manual say its because its cold outside. but it is 80 degrees out. temp sensor on mirror shows correct temp. is there a sepperate sensor for AC unit?
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Posted on Jan 02, 2017
Defrost is the default position. Is the control a autyomatic temperture control unit? ( you set the temp and select automatic) if it is the system is completely electronic. You push the buttons and the control still says defrost or can you select something else and the control shows it but it just keeps coming out the defrost? If the control changes and the air comes out the defrost anyway and the cheack engine light isn't on, then the problem can be blown fuses or an air door actoater not working. Does the dash emit a clicking sound? if it does with the covers off the bottom of the dash reach around touching the different pieces till you touch the idem that is clicking. this is an acutor motor, or blend door motor. they have gears in them that wear out and break the motors aren't repairable and you just replace the ofending motor. the door that is moves can be stuck. and may have to be freed up with blaster, WD40, or other rust buster till it moves easy. maybe after getting the door to move smoothly you can get the old motor to move the door wiithout having to install a new one.
Posted on Jan 06, 2010
May want to look at replacing the wiper circuit board.It is located on the firewall adjacent to the wiper motor and has a some what square black cover with 3 torx screws and wireing harness pluged into the side.We had a truck that every time you washed it the wipers would stay on until it dryed out.You can try removing it and spaying it down with contact cleaner just watch the brease on the two contact tips.Well hope this helps.
Posted on Feb 05, 2010
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