HELP!!!!! Took my truck to town, 19 miles, purred like a kitten. Went out to start it after I was done, and no glow plugs... messed with the wires, tap, tap on relay, but to no avail, so buttercup rescued me. Next day, took the GMC and trailer down to load it up, and the truck started right up, glow plugs worked straightaway, and no problems. However this is nerve racking. It is not fuses, and it works when cool? the controller is new, but you all know how that goes, new bad parts, but it was GM. I think I will take that relay/controller off but? it is sealed, could grind the rivets and take it apart see if anything is wrong inside...What to do...