I recently ripped out an old remote start system that a previous owner (the original owner, I am the 3rd owner) had installed. The wiring they made was a rats nest so I removed it because it wasn't connected anymore and it was a fire hazard. But when I took it out the a/c and heater fan stopped working all together. I have had problems with that before, but I used to just tug on the bundle of wires and something would click and then the fan would run, I think the click was one of the relays the guy had in the bundle of wires. I tried testing the blue wire from pin 8 on the ignition switch, which is the power cable for the fan, and it still sends a signal over to the blower, so that isn't the problem. Is there anything else under the steering wheel that connects to the blower that I am missing? I've tried to remove as much of the plastic trim as possible to see the wires and where they go, but I can't see anything else that goes to the blower from under the dash. Is it as simple as replacing the ignition switch? The guy I bought the truck from said he had already replaced the switch, but with everything attached to the wires the that was connected to the switch, I could see it being a problem. I tried to not remove any wires that looked like they were a factory job. I also tried testing the fan switch itself and all of the wires that go to the motor work perfectly and the switch still works, so I am not sure what I am missing.

 

Probably the ground for the blower switch. Blower should be powered with ignition on, blower switch just provides the ground path. Need wiring diagrams for your truck? Check here..

 

I don't know what the problem was but once I put everything back together the fan was working just fine. Thanks for the help though.