Most likely a bad or disconnected vacuum hose to the defrost/floor selector in the heater ducting.
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.
The doors are electric. You most likely have a broken door inside the heater box under the dash.
There may be several reasons why the air only blows out the front vents and not on the floor or the defrost on the 2003 Dodge Ram. The fuses may be blown, or the heating coil is not working correctly.
A vacuum leak, or one of the doors is sticking/bad vacuum motor in the heater box.
That's probably steam from a leaky heater core.
it could be the heater is leaking!
heater on at idle and will not blow warm air. when moving it blows the warm air from the vents. what will cause this
You lost the vacuume supply coming from the engine, defrost is the default mode if a mafunction in the vacuume supply is lost.
If the heat selector will not switch from defrost to the dash or foot vents on a 1992 Buick, it is possible that the cable connected to the vent is broken. When the selector is moved from defrost, a cable opens the other selected vents on the heater.
Front heater core is in the dash, the rear heater core is all the way in the back of the vehicle. If you have steam coming out of the dash vents, the front HC is leaking. If you have steam coming out of the rear heater vents, then the rear core is leaking.
It's either the thermostat or the heater controls.
The motor which blows air through the vents.
the middle vents only supply air from the ac unit using a separate in dash fan. the floor and defrost vents come only from the heater
It sounds like your air flow diverter is stuck on defrost. Basically it is a little door that diverts the air fom vent to defrost to feet. It could be either the heater control valve, or te temperature selecter cable is broke.
sounds like the vent door that changes the air from defrost to heater is jamed its a little metel door like a flap.follow the cable from defroster switch and you should be at the door,its a manual door
you have to by pass the heater core. get a 3/4 heater connection piece just one way trim your hoses down and then plug off your heater coe connections on your fie wall might try to take out fuse for blower motor if that dont work.you have to bypass heater core very simple thing
The 1984 Buick uses vacuum lines to change air flow from defroster to ac vents. Check the entire vacuum system for leaks.
This is the same on all cars. When the air flow is OFF in a section, the it blows stronger to the other vents. In this case the ones for the windshield. This makes defrosting quicker so you can start driving safely sooner.
why dont bottom vent doors not open on 2001 gmcsonoma
The first thing that you need to check will be the vacuum hoses for leaks, breaks or loose fitting ones.....
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.
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.
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.
Check that the linkage that controls the damper is connected and working. The linkage is just above the gas pedal.