Okay guys, did a search and got a few ideas on what might be wrong, but I'm willing to listen to all ideas. When I first got my truck the heater would only blow on three quarter speed, then all of a sudden it quit. I put power to the motor directly from the battery and it turns on so the motor is good, I replaced the relay, I checked the fuses but don't know which one is for the blower they all looked good but if you can tell me which one is for the heater I will check again, I pulled the resistor and it looked fine but I havene't tried a new one yet, and I put a different switch in (the actual switch on the dash you change the fan speed with) but it was out of a junkyard truck so it could be that. Anything alse I need to check? Anybody run into this before? Thanks for any help, I really miss driving my truck, it's just too dang cold without a heater.
P.S.- It's a 75 K-10