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Coach electrics function when engine is running

September 22, 2012, 10:53:13 pm

Is it normal for the coach 12V electrics to function when the engine is running and the coach battery isolation switch is in the "off" position?  I cannot determine from my manuals whether this should be the case or not.  I have read that the 'fridge will run off the batteries when the engine is running.
BTW thanks for your replies re. my antifreeze question.  I have replaced the old coolant which turned out to be green.  I had asked the question because the coolant in the reservoir appeared to be blue.  I guess someone must have topped up with blue.

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Re: Coach electrics function when engine is running

Reply #1 – September 23, 2012, 08:57:28 am

Marty,

From the factory, it is wired so that the running engine/alternator charges both battery banks through the battery isolator. 

Using the "salesman switch"/disconnect for house batteries does not turn off 12 VDC to all circuits.  Propane detector, refrigerator (at least 12 VDC to the PC board), etc. are not supplied through the switch.

I do not know whether the 12 VDC heating element (3 way refrigerator) is hot with the switch off, but would strongly suspect that it is.

But that brings up the question, why drive with the switch OFF?

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Re: Coach electrics function when engine is running

Reply #2 – September 23, 2012, 11:12:01 am

Marty,
The salesman switch cuts out power to the 12 volt fuse panel that is mounted on the face of the bed base.  Looking at the list of fuse descriptions on my coach it's mostly lights, fans, radio, and furnaces (no frig).  You should be able to tell if your frig is a "3 way" (120vac, propane, 12v) from the controls.  Mine has an indicator light.
The 3 way refers to what's powering the cooling unit.  All model frigs have 12 volt control circuits.  The 12vac and 12v are just heating elements that sit above where the propane burns - so the cooling mechanism is the same for all.  On my coach the frig will not run on 12 volts unless the engine is running (not just ignition) - I'm not sure how it's wired.  Another nice feature of 3 ways is the 30 minute delay going from 12v to propane.  This is a safety feature in case you've stopped the engine to fill up your fuel tank.  I like it because I know I have 30 minutes to level the coach and I never like to have the frig cooling unit operating unless I'm leveled or traveling - important for it's longevity.

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