There is a caseunder the dash that holds the heater core and ac evaporator core. In that case there are what are called blend doors. They are controlled by vacuum from the engine that runs to the doors through a diaphragm. The defrost/floor position is the default position that the blend doors automatically go to if there is a malfunction. Usually when that happens it is caused loss of vacuum. Another sign of a vacuum problem is when there is an apparent loss of air from the dash/side vent position upon acceleration which returns to normal when not accelerating. Annoying but harmless.
That means either you have air in your heater core or your heater core is being bypassed
if you got antifreeze on your windshield when you turn the heater on, it's bad
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
Yes they have a heater/defroster.
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?
it should if you have the heater control in the defrost position this is to remove the moisture from the air
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.
no, I placed a 100w lightbulb underneath the oil pan
Blocked heater core, faulty heater valve, disconnected connection to the heater valve.
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?