I assume it runs all the time anyway because it turns on a few seconds after I start the truck even though the engine is cool and the action compressor isnt on. What gives?

I also have a intermittently working rear power door lock if anybody would like to venture a guess on that

thanks, men!
Brian

 

That fan will only come on if the engine is hot, as seen by the ECU or you have your a/c on. Is it on, if not then you most likely have a bad temp sensor.
As for the door lock, it is starting to fail, what happens if you click it twice, does it then work?