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.
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.
check your vacum line to door by the gas pedal for vacum
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.
depending on what year and make it is, the most likely issue is that you have a valve that moves to divert air to the upper vents, floor vents, and defrost vents and it is either stuck in the defrost position, is broken, or a cable/connector has come loose. The valve is usually in the center of your dashboard up against the firewall. The air flow direction in many vehicles is operated by vacuum controlled servos. If the vacuum supply is cut off, the system reverts to it's default position which is the defrost mode. My guess would be that the HVAC vacuum supply line under the hood is disconnected, pinched or collapsed.
This is a very common problem and you need to check for a vacuum leak, broken vacuum line or a loose vacuum line......
You either have a bad selector switch or a bad vacuum hose at the rear of the engine.
Perhaps a stuck door in the HVAC system or a blockage in the ducts.
vacuum leak the vacuum reservoir is below the left head light, check the hoses
you have a vacuum leak. defrost is the default when a vacuum leak is present.
change the thermostat setting
Check all of your vacuum lines from the ac control panel and under your hood. You have lost vacuum somewhere witch controls your vents. There is one of them loose, disconnected or broken. Should be easy to trace. Good Luck!!
Any of the following can cause this......... 1. Bad a/c - heater controller.. 2. Bad a/c - heater controller inside door operation.. 3. Bad, broken or cracked vacuum line/lines..
I don't know why the vent would not open for the defrost, but it may be related to the fact that your heater core is blown. If your getting nothing but cold air out of the vents when the heat is on, your core is finished and if the core is finished then it is likely related to your vent not opening/switching. Something''s wrong with your heating either way.
An air conditioner evaporator is the part of the a/c system that the heat in your car transfers to causing cool air to blow from your vents. The blower is in front of it and it sucks air from the inside of your car and across the evaporator then blows out your vents.
on my 1992 road touring itdid the same thing and it was the computer but it only cost 102.00 from gm
Moisture in the air condensing into mist.
I had a Chevy van of this vintage and I found a vacum hose leak in the controls that would make the heater/defrost door default too defrost open. lisining carefully under dash or under hood may pinpoint leak. I had a Chevy van of this vintage and I found a vacum hose leak in the controls that would make the heater/defrost door default too defrost open. lisining carefully under dash or under hood may pinpoint leak.
most vehicles use a vacuum diaphragm to move the mode door inside the dash from the floor to the vents to the windshield. Either the vacuum diaphragm is leaking or the vacuum hose has become disconnected. In my 85 topaz the door pannel vents are used to defrost the side windows.