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Old 05-18-2014, 08:34 PM   #1
Winnebago Camper
Join Date: Aug 2010
Posts: 19
Wiring Coach vs Engine batteries

I read a lot of the posts regarding Coach and Engine batteries. None touch on the problem I'm experiencing.

I just returned from a trip where I had to replace both coach batteries. While in the process I checked the voltage on the Engine batteries from the panel within the coach. Interestingly the Engine voltage reported on the COACH battery display - not Engine! Hmmm. I also noticed that my 12v systems would quickly discharge the batteries and since the Engine batteries don't charge from Ground Power I had to use a charger (yes, I use a disconnect switch when charging).

When I bought this coach (preowned) the batteries had been changed by the dealer. I had no reason to believe anything amiss. Now that I've had some failures I'm noticing anomalies.

I checked the Winnebago wiring diagrams but they're not real clear on what gets connected to which batteries. The Owner's Manual says ONLY the Engine and dash panel operate off the Engine battery. If so, why does my fridge show low DC voltage and my 12v lights dim and fans slow when the voltage on the Engine batteries runs low? I'm guessing something is not connected correctly.

On my 2 sets of batteries one has a rats nest of wires. These are currently the deep cycle batteries. The "normal" batteries only have 2 large positive and negative wires. Could it be the positive wires from one set of batteries was reversed with the other? Would it be as easy as disconnecting the Engine batteries and trying to start the motor to see if this is the case?

Your thoughts would be appreciated.
Larry & Phyllis
Santa Fe, NM
2003 Winne Journey DL
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Old 05-19-2014, 04:24 AM   #2
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Posts: 26
A VOM/Multimeter will tell you which set of batteries are being charged by the engine alternator, or are not being charged. Simply check voltage at the battery(s) with the engine running and with it not. Quite frankly this is one of the arguments for using a batter monitor which will tell you the state of charge of both the starting batteries and the house batteries.
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Old 05-19-2014, 06:26 AM   #3
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Location: Home on the hill in Georgia
Posts: 296
Sounds like something could be wired wrong. Agree with above post, a good voltmeter is a must for checking electrical problems.

Contact Winnebago Customer relations, they can probably send a detailed wiring diagram. Winnebago Industries
Jerry & Patsy Potter, Taz & Jake Jr.
2000 Winnebago Journey
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Old 05-19-2014, 06:27 AM   #4
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A VOM/Multimeter will tell you which set of batteries are being charged by the engine alternator, or are not being charged.
Same can be checked when on shore power.
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Old 05-19-2014, 06:01 PM   #5
Winnebago Master
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Location: Buxton, North Dakota
Posts: 1,037
It would be better to measure the voltage while on shore power with the converter charging the house batteries. With the engine running both batteries should be receiving a charge and show the same voltage. It does sound like they are reversed. You could have a defective battery isolation solenoid, if so only the chassis battery will show the charge with the engine running.
2003 Winnebago Adventurer 38G F53/ V10 605 watts of Solar
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1999 Jeep Cherokee & 1991 Jeep Wrangler Renegade
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Old 05-19-2014, 06:17 PM   #6
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Location: Powell River, B.C.
Posts: 339
If you think the positive cables have been crossed up, safest way to check this out would be to track from the starter to the battery bank. Yes I know it's a mass of black cables but grab a roll of red electrical tape and put a wrap around the cable as you go. I have taken to wrapping chassis positive wiring with red tape and coach positive with white, because I can't remember one time to the next which group of wires is which.
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Old 05-20-2014, 05:48 AM   #7
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Location: Indian River, De
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As advised, use a meter to determine which bank os being charged from shore power and engine alternator. And yes, you can simply disconnect one bank and then see if the engine starts from the other one (assuming you battery parallal solenoid is not stuck closed).

Engine alternator only charges engine batteries. Shore power only charges house batteries. That was one thing that bugged me when I first bought my coach, unless the dashboard battery parallel button is held in. I think Winnebago changed that arrangement on later model year coaches, but my 02, and I think your 03, are the same.

I replaced my parallel solenoid with a Blue Seas smart switch, so that low batteries first, then all batteries, are automatically charged from any source, whether it be shore power, engine alt, or generator.

BTW, Skip's suggestion is excellent.
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batteries, wiring

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