I have an 86 chevy k20 that I recently purchased. I'm currently finding all the bugs and working on fixing them. One that I have is that the ac/heater fan does not blow on low and medium. Yet it blows just fine on high. I THOUGHT it would be the resistor. But other Googling I did makes me think replacing the resistor will only fix the issue if it was the HIGH blowing wasn't working.

help?

 

Go back to your original thinking.

High speed is a totally separate circuit incorporating the relay. Look at the fuse, switch and resistor.

Allan

 

I have a 2004 Trailblazer that this summer, the high(5) speed stopped working in my AC vents. Now it's winter and none of the speeds work to blow the warm air. I can feel the warm air at the vent, but it won't blow anymore. Also, the lower heat/AC vents haven't worked in quite some time. What could be the problem?