Aqua Hot while driving …does preheat switch need to be on? - Printable Version

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+--- Thread: Aqua Hot while driving …does preheat switch need to be on? (/showthread.php?tid=8792)

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Aqua Hot while driving …does preheat switch need to be on? - Gem930 - 12-21-2025

I guess the title says everything… about to start a trip for Christmas and I am not sure if I have to have the engine preheat switch on in order to take advantage of the engine heating the aqua hot?

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RE: Aqua Hot while driving …does preheat switch need to be on? - cwl1979 - 12-21-2025

Nope. The engine water pump will do its thing for you.

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RE: Aqua Hot while driving …does preheat switch need to be on? - Gem930 - 12-21-2025

Thx!!! I figured that was likely the case, but just wanted to be sure.

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RE: Aqua Hot while driving …does preheat switch need to be on? - Richard - 12-22-2025

Its a good question. On my 95, there was a booster pump in addition to the engine pump. It kept the coach toasty while driving. The 99’did not have the booster pump, and would not keep the AH system warm enough to keep the interior comfy. Using the engine preheat switch helped a good bit to keep it comfy. But in really cold weathe travel, I turned on the diesel burner.

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RE: Aqua Hot while driving …does preheat switch need to be on? - cwl1979 - 12-22-2025

My 96 has the booster pump for dash heat as well. I did forget to turn of the Diesel burner one morning on the drive across the country and promptly overheated things. Engine temps wouldn't get below 210. I had to pull over and let things cool off. Thats when I heard the diesel burner kick on, shut it off and problem solved. Right back to 185 where it should be.

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