Viper31

Got a 2002 Chevy 3500 Silverado last year, my first Chevy truck. I drove this thing to my parents house on Thanksgiving weekend to log some miles on it as it sits most of the time in the winter. The weather was real crappy with lots of rain and temps dropped quickly. I was having some problems keeping the windows from fogging and realized the HVAC controls will not allow you to turn off the outside air unless you turn the selector to the vent position. WTF, I thought something was broke until I read the owners manual and sure enough that is how it is designed to work. Are all Chevy HVAC controls like this? I have owned many vehicles over the years and none of them had HVAC controls in which you could not control the outside air regardless of the selector position.

Wobble

Sounds like you have a vacuum leak check the line going to the vacuum reservoir, not unusual for them to crack with age and heat. Stops the flaps from working as they should.

You should be able to select outside air except when using max a/c. On defrost it will stay open.

handfulz28

Viper, my '01 Yukon is the same way. If you set it to blow out the defroster vents, it forces you to use outside air. I think it also might do that if you turn on a rear defroster.
Yeah, first vehicle I'd seen do that too, but it actually defrosted my windows pretty quick.
Thanks,
Michael

dmaxx3500

they do that so your are getting dry air , not the air from inside ,,too much condensation