It's electrical. Requires upgraded or dual altinator. Operates automatically, turns off and turns on, depending on the temperature of the engine. If the engine is warm enough, the cab heater does not turn on.
From what I read, I believe it is on allthe time with the heat, and increasesthe heat output of the truck, something like max heat, I do know that it is an electrical heat strip. As mentioned previously, it requires upgrade to standard altenator.
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