[kwmech]

Sure could be the controller, a loose wire somewhere. Controller manages the ground in the system, meaning that when you turn on the ignition that little brown/white wire that goes to the relay is excited. The controller measures engine temp and times the amount of duration that the relay stays on. Does that make sense? anyways a fool proof way is to run the black wire on the relay to a push button that is connected to ground on the other side and go that way. Just hold the button down when needed---but not more than 5-6 seconds at a time when cold