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Old 12-23-2018, 12:39 PM   #1
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Default Chevy Dashboard Battery Light Came On!

I've got a 2004 Chevy Express based Roadtrek. Last night, on a 5 hour trip south, we stopped for gas halfway and upon getting back on the highway I saw the little red light on the dash for my battery, I also noted my battery was at 11 volts! I planned on exiting the asap but the light went off and the readout was at 13.9 volts. It stayed off the rest of the trip and mostly at 14 volts. It was cold and I had the heater fan blowing full blast most of the time. When I reached my destination I noted that with the engine off the battery was reading 12.4 volts. Has anyone had this happen to them? The battery is a cheapo Walmart I've already replaced once. I suspect it is the problem.
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Old 12-23-2018, 01:10 PM   #2
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I've got a 2004 Chevy Express based Roadtrek. Last night, on a 5 hour trip south, we stopped for gas halfway and upon getting back on the highway I saw the little red light on the dash for my battery, I also noted my battery was at 11 volts! I planned on exiting the asap but the light went off and the readout was at 13.9 volts. It stayed off the rest of the trip and mostly at 14 volts. It was cold and I had the heater fan blowing full blast most of the time. When I reached my destination I noted that with the engine off the battery was reading 12.4 volts. Has anyone had this happen to them? The battery is a cheapo Walmart I've already replaced once. I suspect it is the problem.
Last year I installed a battery cutoff switch which was behind the battery such that you kind of just forgot it was there. It went bad over a short period of time and resulted in odd voltages. Mine chassis is also a 2004.
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Old 12-23-2018, 09:23 PM   #3
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Sounds like you may have a loose wire on your alternator and not making contact. I would check for loose wires on the alternator and on the battery. It could also be a bad ground wire that jars loose or is loose and drawing a lot of current running the heater on high.
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Old 12-23-2018, 09:35 PM   #4
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Sounds like you may have a loose wire on your alternator and not making contact. I would check for loose wires on the alternator and on the battery. It could also be a bad ground wire that jars loose or is loose and drawing a lot of current running the heater on high.

You might have an battery isolator that is failing intermittently. When the low voltage is present, you would just need to check the input to the isolator and see if it is the same as the low voltage at the battery. They should close to the same, with the battery being about .7v lower.
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Old 12-24-2018, 12:03 PM   #5
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You might have an battery isolator that is failing intermittently. When the low voltage is present, you would just need to check the input to the isolator and see if it is the same as the low voltage at the battery. They should close to the same, with the battery being about .7v lower.
in this case, would bypassing the isolator allow me to continue driving?

BTW do you know if the alternator is the 145 version in this Roadtrek of mine (2004 Chvey)?

Thanks!
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Old 12-24-2018, 12:19 PM   #6
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in this case, would bypassing the isolator allow me to continue driving?

BTW do you know if the alternator is the 145 version in this Roadtrek of mine (2004 Chvey)?

Thanks!

Yes, bypassing the isolator would get you going if it is the problem.


AFAIK, all the Chevy Roadtreks of the 2003 and up vintage used the 145 amp alternator.
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Old 12-24-2018, 08:20 PM   #7
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in looking at the isolator, it is not clear to me how i bypass it

is there a diagram somewhere online?
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Old 12-24-2018, 08:46 PM   #8
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in looking at the isolator, it is not clear to me how i bypass it

is there a diagram somewhere online?

Hopefully, some others are familiar with that particular isolator to know the connection locations. The goal is to get the cable from the alternator connected to the cable to the starting battery. You likely can just move the alternator cable to the same stud as the starting battery is on.
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Old 12-25-2018, 02:54 PM   #9
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so now the question is where do I get a replacement isolator? and given Roadtrek has switched to separators, should I get one of those instead? Would I be able to use a separator with existing wiring? TIA & Merry Holidays!
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Old 12-26-2018, 02:42 AM   #10
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Default Isolator bypass

Bypassing the isolator is relatively simple. You need to disconnect both batteries first! With the batteries disconnected, note the 3 large terminal studs on the front of the box. Using a 7/16 inch box wrench (or an adjustable) remove the wires from the outer terminals and put them on the center terminal. In other words, all 3 large wires are on the center terminal. Everything will operate normally with one caveat: since there is no longer isolation between the 2 batteries, you must be careful when boondocking to not run the batteries down to the point where you no longer have power to start the engine.

Replacement isolators are readily available at marine stores, RV stores or over the Internet. You will need an amperage model equal to or greater than your alternator rating. On Chevrolet chassis it is 145 amps. I am not sure regarding other manufacturers chassis but it will be similar. You can also convert to a separator relay.
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