More Heater motor problems... only one speed. What needs replacing?
My heater motor problems in my 1983 F100 continue... I thought I had all three speeds but it apears I only have high speed (fast and noisey!) which isn't too bad for the winter.
As you might recall, we had a 93cm (40in) snow fall; a real blizzard. The cowl and heating system was plugged with snowand when the truck was turned on the heater motor switch was set on the middle speed. Well I guess the motor couldn't turn because of the snow and I started to get smoke through the vents and a strong burning smell. I switched the blower off and the smoke and smell went away, Now I only have one speed... high.
My question is what do I replace to get all three speeds back? Just the motor or is it the switch in the dash?
Most likely its the blower resistor. The resistor is what limits the current through the motor to make it run at the lower speeds. It is bypassed by the blower switch for high. Do a search on resistor and you will find a lot of information.
I just looked in the Haynes manual, and they show the resistor assembly mounted below and to the right of the blower motor. All you will see from the outside is a big plug with wires going into the heater plenum. The resistors are mounted on the inside of the duct so the airflow will keep them cool.
It is most likely the resistor but before you spend your hard earned dollars it might be a good idea to check it with an ohmmeter. You should have continuity between all the terminals. If you don't then buy a new one.