So I was driving my FC the other day and I went to put the heater on a little bit. But as soon as I turned it on, it went full blast. I tried the slider adjustment but i stayed on full all the way until I turned it off. It's done this before, but some days it would go back to normal. Help?

 

Swap the logicon out with another one. It's probably going bad. Mine cuts the blower on and off randomly so I have to keep on tapping it due to a bad relay.

 

Sounds like the board in the air mix motor is bad. It tells the logicon where the mix is currently set. Or the logicon is broken. Same cold solder technology that makes the idiot lights go bad.