There is a vacuum switch that controls an air gate that diverts the air flow to the proper outlet. Blowing air out the defroster is the default setting of the switch. Most common causes of this problem are vacuum leaks. Check the vacuum hose on the passenger side engine compartment first. It ususally leaks going through the fire wall. Regardless this problem is most often always the result of a leak somewhere in the vacuum system not the failure of the switch itself. If it is a diesel check for proper operation of the vacuum pump
That's probably steam from a leaky heater core.
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.
Most likely a bad or disconnected vacuum hose to the defrost/floor selector in the heater ducting.
Over time debris and other things can collect near the heater core, its possible that something small and plastic has fallen down through the defrost vents and gets hot when the vehicle is running. You may need to disassemble the heater and remove the items and perhaps vacuum it out.
The year, make and model would help but many vehicles use vacuum to operate the direction of air flow through the floor vents, dash vents and defrost vents. If the vacuum supply is cut off for whatever reason the system defaults to defrost only. So if you only have the defrost mode working chances are the vacuum supply is cut off. Check the HVAC vacuum supply line under the hood for damage. If that system seems to be working but you have insufficient air flow through all of the vents, check/replace the cabin filter if applicable.
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.
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
When there is a problem in the vent system it defaults to defrost setting. Check the doors & vac supply
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.
Most people when they say "air filter" are referring to the engine air filter. Cabin air filter cleans the air that comes into the car, goes through the heater core or air conditioner and then out through the vents into the cabin of the car.
Your rodeo has 3 actuators. One is for your evaporator(cool air) another for your heater and the other one controls your defrost , face and lower vents. These electrical actuators are about the size of a donut and have a hole in the middle with a bushing which engages with your vents, located under your dash board on the passenger side.It may take alot of unscrewing and alot of patience, but its the only way to solve your problem.
The doors are electric. You most likely have a broken door inside the heater box under the dash.
The heater blower may not be working properly. Without the heater blower working, the air will not come through the vents.
it could be the heater is leaking!
2003 crown vic air conditioning vent dont blow
Probably a vaccum leak. The vents default to the defrost vents (Windshield) when there is no vaccum. The main vaccum connection is on the throttle body. The thin lines become brittle and break very easily. Good luck finding the leak.
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.
Check that the linkage that controls the damper is connected and working. The linkage is just above the gas pedal.
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.
this one is easy your switch the controls the vents is not working there is a flap the closes the defrost vents so that it goes through the other vents or there is a vacumn line that is controlled by the switch, and its leaking. The vacumn line is usually on the engine side of the firewall. It is a very small plastic tube comming out of the middle of the firewall at the top and it connects to a junction with other vacumn lines. See if any of them are disconnected.
Idk know but mine does it when i start off from a red light or stop sign and as soon as i let off the gas or it changes gears (automatic) it comes through the vents like normal.
If central air conditioner turns on but is not blowing through the vents, check the filter. If it is dirty, change it. Change the thermostat into cool, this will defrost the air conditioner.
Because the air selector died.
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
Does air come out at defrost vents? Defrost is the default position. 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