I have read that the blower motor resistors in these trucks will burn out, and the blower will only operate on the highest setting despite the switch position (hi/lo). Well my resistor is still good, but no matter what setting my switch is on, my blower barely blows any air. Can anybody help me? I'm guessing it's either the switch or the motor itself. Could it be anything else? Truck is an '89 250 7.3 by the way....

 

What happens when you switch positions on the controls? Can you actually feel the air divert correctly?

When I got mine the foam was shot everywhere on the doors, the main diverter door was broken and not able to do anything and one of the other vacuum podges was physically jammed up under the dash. I had to pull everything apart to clear crap out, refoam and make my own hing on the main door. Now it works correctly and I also cleared out all the cowl areas.

 

On my 89 the blower motor didnt work either. I found the fuses ( a lot of other fuses too) were blown. I hooked up the motor directly to the battery (its right in the right side of the engine compartment) and the blower worked. I put a switch in so now you start the engine, raise the hood, flip on the motor and presto heat and defrost.

You just have to turn it on and off from under the hood.

Even so the allowcation of the heat still works ie you can switch from defroast to passenger compartment with the controls.

 

Check voltage and ground at the motor. If you have battery voltage and a good ground on high the motor is bad.