HVAC blower questions...

[1988ssp50]

Does anyone know what would cause my blower to only run in the high position? In the other three positions nothing happens, but in high it blows on high?
-Chris

 

[Saleen0679]

Sign of a possibly bad blower motor resistor.

 

[PuterAmI]

Saleen0679 is very close. You have a resistor pack that contains three resistors. When the fan speed is LOW, current is directed through all three. On MEDIUM LO, through two. On Medium HI, through one, and HI none.

There are current draw tests in the manual for the motor.

 

[Saleen0679]

Sounds like we're talking abou the same think PuterAmI. The shop manual calls the resistor pack a blower motor resistor or a blower resistor. It contains three resistor coils and a thermal limiter mounted onto the blower motor housing.

 

[PuterAmI]

Yep. I got mine from the 87 Ford shop manual.