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
It is for vacuum storage. It keeps blower mode from switching to defrost when accelerating. The mode selection is vac controlled and will default to defrost when vac is lost or low. This stored vacuum keeps that from happening
How do you replace a defrost blower motor in a 2003 Toyota Corolla
blower fan location on a 1979 lincoln
No, the rear defrost is just an electric grid on the rear window. No air movement involved.
blower motor resistor is burned out
If you are talkiing about the blower motor inside the vehicle it is under the dash pad and under the defrost duct
Remove the wiring harness from the back of your 1986 Lincoln air conditioning blower motor. Remove the blower motor retaining bolts. Remove the fan on the front of the blower motor. Reverse the process to install the new blower motor.
It is located under the dash near the blower motor.
If you are sure the blower is working and pushing good air flow, it could be the air flap that changes the flow from defrost to the floor or to the vents is stuck. It may be partly open but not all the way and only allowing limited air flow.
Faulty Function selector switch. Consider replacement.
Defective blower motor resistor module. this is true except if the control module is malfunctioning at which point the defrost goes to emergency mode in which the defrost will stay on permanently. My module will not power up and I need help with wiring schematics to find a bad ground or power wire
Most likely it is a resistor that has blown on the back of the controls.