My fan only works on high speed. Is there something I can check to get the lower speeds working again?

 

It's almost certainly the resistor.

.

Pull the 2 screws holding the plate in the blower box, pull it out, & test across the thermal fuse (the only thing that's not a coil of wire). If it's an open circuit (infinite resistance), it's dead. Buy a new resistor. Before installing it, test the current draw of the blower motor (should be less than 22A on HI) or you could burn up the new one. Then clean all the leaves & crap out of the box & off the evaporator core.



If the fuse is OK, you'll have to do some diagnosis on the wiring between the resistor, the motor, & the control panel.

 

Good info. Usually one of the coils will be broken or burned thru.

 

If it was one of the coils, only that one speed would be affected. For all of them to be dead, it's most likely the fuse. Hi doesn't use any resistors, so that's why it still works.

 

I have a problem and need help with what to look for .
my A/C started blowing hot so i checked and the compressor is working fine.I though it may be low on freon but then i noticed it even blows very hot when just on vent.
Is the heater control switch bad or is there a valve or any other thing that could be bad.Is there a way to test the switch to change it from hot to cold?
Any help would be appreciated.

 

How could we possibly guess??? You haven't filled in your profile, or told us anything about your truck.