If defrost is on it could be your compressor going bad. See what happens when you leave off defrost or disconnect your compressor. It only controls defrost and air conditioning. I had the same problem
That means either you have air in your heater core or your heater core is being bypassed
You have a vacuum line disconnected probably under the hood. The HVAC controls are operated by vacuum and when there is no vacuum it system goes into defrost mode.
most likely your heater controls run via vacuum lines. cracked or broken lines could cause this.
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.
press n hold the off and warmer buttons on heater controls while key is on
I would think that is a vacuum or a linkage problem with the heater control assembly (where all the buttons/slides are for changing between floor/defrost/vent) Had a diaphragm go bad on one once, and in a jeep cherokee, a slight collision with a guard rail knocked a vac line off for the vent controls, and ac only worked from defroster.
a heater hose runs from intake to heater core to radiator. the heater core is were the heat comes from inside the car as well as defrost
Don't know what vehicle you have but most HVAC controls operate from a vacuum supply from the engine. I would start with checking the vacuum supply connections under the hood. They could be cracked or disconnected.
Many cars use engine vacuum to operate HVAC controls. If vacuum is cut off the system defaults to the defrost mode. Check the HVAC vacuum supply hose under the hood leading from the engine. It may be disconnected or damaged.
Push the rear window defrost button , located with your heater controls , that also heats your exterior mirrors
ihave a 1986 chevette that when i turn defrost on it blows out heat and when i put heater on it blows out only cold air? ihave a 1986 chevette that when i turn defrost on it blows out heat and when i put heater on it blows out only cold air?
Yes, the overhead heater controls do light up.
the heater controls are run on engine vacuum. When a engine is accelerating it has a drop in vacuum. There is a one way check valve that keep vacuum in the heater circuit that has gone bad. You could have it fixed or you can deal with it, its not that big of a deal
Yes they have a heater/defroster.
The fastest way to defrost a windshield is to turn the defrost vent on without heat or simply open the windows. Another option is to warm the inside of the car by turning the heater on.
it should if you have the heater control in the defrost position this is to remove the moisture from the air
Blocked heater core, faulty heater valve, disconnected connection to the heater valve.
Some will, most wont. The A/C button should, but the others you'll need to learn in the light and remember for night driving.
Yes, the ac will run in the defrost position to dry the windshield.
Most likely a bad or disconnected vacuum hose to the defrost/floor selector in the heater ducting.
2001 dodge ram 1500 ac and heater flow regulator switch does not work. works only on defrost. How to fix?
More than likely its the defrost timer or the defrost heater. You can try and advance the timer which is usually located at the top of the refrigerator compartment. Its usually a small round circle with a slot in the middle. Take a slotted screwdriver and advance it till you hear it click then stop advancing it. This more than likely is defrost mode. It should kick on the defrost heater. Listen closely if you can hear the heater kicking on and sizzling the ice. If you do advance the timer to run after about 1/2 an hour and repeat the process until the ice is gone. If this works then the timer is defective and needs replaced. If this process doesn't work then the defrost heater is probably defective.
The relay for the heated rear screen on a Golf MK4 should be just below the heater controls on the dash. Look for a button that says rear defrost or something to that effect.