I would lean toward the blower motor itself or maybe a loose wire since it starts running when you hit a bump.

 

Well see, thats what throws me off. If it was a bad resistor or something along those lines, would it periodically work like it should and then all of the sudden quit? Then when I hit a bump it starts working again?

 

Its really going to depend of it there is a break in the wire somewhere. this could be inside the resistor block or the electrical wiring to the motor or inside the motor windings itself.

You hit the first bump and the wires move and loose contact. Then you hit the next bump and jar things again and the wires touch and the fan works......get it?

 

Yeah, that makes sense I guess. I will still havta get my electrical guru on it though to see exactly wear the issue is at...

 

I had the same problem on my 04.5 2500 5.9L RWD (blower motor worked when it wanted to), but I found it came back on when I tilted the steering column. I chased that to a plastic rotary switch in the column that had overheated at the plug connector (charred black). I replaced it and now two years later it has over heated again. Try looking there too.