[qcj]

Richard, My AH is always hot after driving. How the engine heat gets there I don't know but will check and see if there is a pump or something. I do not activate the engine preheat. The water temp. is never as hot as the engine temp. but is about 160-170 degrees.
I just figured that the engine water pump fed the water to the AH. Have you checked the four cut offs with the black handles that feed water to the AH and the dash heater?
I had to replace this set of 4 cut offs this last year.