Yes both are used in pre-heat mode. Post heat mode can use both or alternate one then the other, depending on the temp. The FSM doesn't state at what temperature set point it will go to alternating. In the post heat cycle there are periods when both heaters are off. That is why your head lights & alternator gauge show normal voltage levels.
Last edited by Paychk; 11-19-2005 at 11:03 AM.
04 2500 Laramie Crew Cab Short Bed Stock 91,000
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