What causes dual air conditioners on 2004 Chevy pick ups to revert to heat automatically?

Answer 1

I had this problem with my Silverado. There are two small motors mounted on the bottom of the air ducts. They control doors(?) that separate the cold air from the hot air (heater core). These motors used to function off of the vacuum from the engine. GM changed these motors to electric. To check these you will have to remove the cover from the duct . The cover has six or seven bolts holding it in place. The ones over the trans hump are a pain! Once you have the cover removed the motors are easy to see. They are about an inch and a half to two inches thick (kind of small) and black in color. Remove the motors, take the case off, clean and put the di-electric grease (will not work with out this) where the contacts touch the board. Connect the wires turn on the ignition and function test. If this does not fix the problem I would check the fuses under the dash and hood. If both passenger and driver side are blowing hot I would think it is a fuse issue. I had these priced at a Chevrolet dealership at $254.00 each. They are proud of them. Hope this helps!