Anyone know about battery constant isolators

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Anyone know about battery constant isolators

Unread postby mattiosmaximos » Sat Aug 04, 2018 2:07 am

I think I tracked my no power to the coach when parked problem. The 3 prong isolator that goes to the dual/ mom switch may be dieing. I get power to the back when plugged into 110 or when the engines running and the dual switch is on but that's it. I don't know much about isolators but I know mine has the right post going to the coach battery, the middle going to the alternator and I think the left goes to the ignition and main battery. Are these things 80amp? Are they single or double? Are all 3 posts the same? 86 turbodiesel.
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Re: Anyone know about battery constant isolators

Unread postby IdahoBob » Mon Sep 03, 2018 2:59 am

The 3 prong isolator is a simple high current relay sometimes called a contactor.
When there is 12V applied to the center contact (coil), the left and right are connected. The other side of the coil is chassis ground.
You can check for 12V in DUAL with the engine on (center contact powered by car battery), or in MOM (entary) at any time (center contact powered by the house battery).

Not sure about offical tests, but a good one is to look at the voltage drop with and without. I would expect sub 1/3 volt when connected, and anything goes when not. A clamp on DC amp meter is really helpful to see how much current is flowing.

The contactor has nothing to do with the 110V Converter. It does it's own thing with the house power and the house battery. It's located in the AC DC fuse panel near the furnace. It's what hums when you have shore power and is located in the bottom half below the 12V fuses.

I hope that helps. If more questions, feel free to ask. (I've put WAY too much time into the 12V house circuit of my 84 TD)

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