Vacuum leaks in the A.C. system. DO YOU hear a faint humming or whistling sound?
why dont bottom vent doors not open on 2001 gmcsonoma
If you are refering to the vents near or on the door try toggling the switches near the steering wheel. One is marked L and the other R. You can move them up or down.
it is the moter that spins the fan that blows your heat or ac out of your vents
Cold air from the defrost indicates that the air doors are in the wrong position. The doors are vacuum controlled in most vehicles. check the vacuum system for a leak.
Your average A/C unit blows heat through all vents.
i own a 90 olds 98 it had the same problem u have to take the bottom part of the dash off and check for any vacume leaks
The heater may not be on - but the fan still blows air through the vents when they're open !
The question you ask is too involved for a proper answer. You need to go to a car parts store, and get a repair manual for your car. They cost about $16.00 Or, go to a Public Library.
Usually is a vacuum problem. The vacuum works through the climate controls to make the vent doors open and close.
Check for a vacuum leak either under the hood or under the dash Check the operation of the vacuum actuated motors under the dash Check the operation of the selector switch at the dash
My ac blows only in the defroster and not any of the other vents i have 98 ford windstar 3.8 v6
If your 03 Trailblazer blows heat out of the back vents when set on AC sometimes, it could be because of a faulty blower motor resistor block.