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Discussion Starter · #1 ·
So when I first had my auxillary battery and isolator installed (local garage did it as I was getting nervous about it), the battery warning light would come on if the auxilliary battery had been drained down a bit. Odd thing is if I stopped and turned the van off, and then back on again, the light wouldn't reappear. I had the shop check things and they assured me everything was working correctly.

Over time the issue seems to be more and more prevalent, with the light coming on everyday on first start up, but still going away if I stop and restart, which is what I've been doing.

So two questions, one am I doing damage? Two, what would I test to see if there is a real world issue?

(To clarify a little, the light comes on normally on start up, then goes off normally after a couple seconds, then comes back on after a minute or two of run time.)
 

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Measure the voltage. Maybe you could clip on some leads and keep an eye on it. Best if you measured it near the main battery, but near the aux battery is probably good enuf and probably easier to do.
How big is your battery and how deeply discharged is it when the battery light comes on? It could be coming on a minute or 2 after run time because that's when the isolator relay closes and the aux battery starts taking current. I suppose it could happen if you have a very large, discharged battery and the alternator can't supply the current and keep the voltage up. It's never happened to me though and I have a 150 ah battery and have had it discharged quite a bit.
 

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Discussion Starter · #3 ·
Thanks. Its only a 135ah battery, and it's not very deeply discharged, just sitting overnight with no real draw.

I'll mess around with it this weekend and see what kind of voltages I'm getting. Do you know what the battery warning light is sensing, volts or amps?
 
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