you have a problem with the vent door flap.
answer if your heater and a/c are intergrated, you may have a leaking heater core
I thought the 2002 Saturn SL2 computer responsible for air conditioning and heating had failed, because the air conditioning comes on when I put the vent position to defrost (I'd never noticed this before and had experienced other problems with that computer in the past when it had been programmed incorrectly.)
I took it to the Saturn dealer, and the service receptionist had never heard of it. The service technician informed us that the air conditioner comes on by design, to remove humidity from the air. The only problem with that, of course, is that in very cold weather, the humidity is frozen out of the air, and you'd like as much heat as possible on the windshield.
Anyway, maybe someone else will appreciate the strange answer. I personally would like to choose whether to use the air conditioner in the dead of winter!
Add on, Also I was told from a dealer once that the reason the airconditioning pump comes on when the defrost is selected is that the compressor for the airconditioner needs to run every so often. During Summer it is expected people will use the airconditioner and so it is used frequently, however in winter the airconditioner could sit inactive for some time. We regularly use our defrosters with heat in winter and that is a good time to run the airconditioner as well.
You probably have a jammed or otherwise defective vent door.
The vacuum supply line from the engine is disconnected or broken. When the vacuum supply is cut off the system defaults to the defrost mode.
the heat blows out the defrost when it should blow out floor vents only
check your vacum line to door by the gas pedal for vacum
on your car it is a defalt mode for air to blow out defrost when there is no vacumn from the engine so you should look for a broken vacum line or see if it has come unplugged on the engine.
The air of your Chevy trailblazer 2004 blow out of the front vents when the air conditioner is on because the air condition is faulty and it needs repair.
hi i like nomey
2003 crown vic air conditioning vent dont blow
Coming out of the vents around 43 degrees
The AC does not blow on the main front vents. Only rear and defrost.
Because the air selector died.
This is a very common problem and you need to check for a vacuum leak, broken vacuum line or a loose vacuum line......