Why does your heating-ac only blow out of the defrost 1990 Jeep Cherokee?

Answer 1

There are two possible solutions. ffirst is the door may be locked open where the exchange takes place for the direction of flow. Second is the vaccumm valve that operates the door. It is usually located under dashbut you can check vaccum canister to make sure there is enough vaccum.

Answer 2

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

answer

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.

Answer 3

The doors that control the airflow are in turn, controlled by vacuum operated actuators. When the airflow defaults to defrost, it typically indicates that the source for the vacuum was lost. Check under the hood, near the firewall, for any small hoses that may have come undone.

Answer 4

check your vacum line to door by the gas pedal for vacum

Answer 5

this system operates using the engine vacuum. it could be a vacuum leak .

Answer 6

Prob the control switch. I have a similar problem with a 1993 Taurus. U put it on ac it blows out def. Def. blows out vent and none of it really blows out unless it's on high.

Answer 7

You either have a bad selector switch or a bad vacuum hose at the rear of the engine.