My first, original problem was that the heat would randomly work on and off, then after my truck was shut off, my heat would not shut off. The only way to stop it was to disconnect the battery, now my heater stopped working and after my truck was shut off my lights would not shut off. I played with the DRL nob and nothing happened, then I shut my fan control switch off and my lights shut off?
If you fan doesnt' work the harness is probably burnt up tha thappens in these trucks if you get the harness from gm parts direct and resistor it's about $100 but you have to install it. Make sure that is the problem first though. Check yoru fuses for drl they normally only work when you put it in gear.