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Ask Dave: Nothing 12-volt inside RV is working. What to check?

Dear Dave,
I am having an electrical problem with the interior coach lights, the generator switch, the tank level monitor—everything that is 12-volt DC current. The coach batteries are at full charge and the fuses are not blown. The OBD reader shows no codes. I am at a loss as to what to check next. Thank you. —John, 2001 Winnebago Brave

Dear John,
In the 2001 model year, Winnebago had seven different floor plan models/lengths for the Brave. All came on a Workhorse chassis ranging from 12,400 lb. GVWR to 18,000 lb. GVWR. All had a Vortec engine, which typically had a GM-supplied battery. It most likely has been replaced.

The house batteries were two 12-volt batteries connected parallel, which means positive to positive, negative to negative. It gives you a 12-volt power bank and doubles the amp hours. I guarantee these have been changed from the originals. All three were originally stored in the battery compartment under the entrance steps, like this 2001 Adventurer that we have done extensive work on.

You did not identify what exactly your electrical problem is. However, you indicated: “the interior coach lights, the generator switch, the tank level monitor—everything that is 12-volt DC current”—so I assume none of these are operational? Then you stated the coach batteries are at full charge, no blown fuses, and the OBD reader shows no codes.

Batteries in the RV

I believe you are misinterpreting what battery or batteries run the various components in your rig. The engine or start battery is rated for cold cranking capacity or CCC and supplies power to the starter and engine components. It is the battery on the right side of this photo.

The house batteries are deep cycle batteries that power the interior lights, roof vents, monitor panel for tank levels, and any appliance that runs on LP. The 12-volt power goes through fuses for each application. In your case, Winnebago uses push button fuses rather than the automotive type others use in a distribution center. In the photo above, you can see the white push button fuses in the step compartment. I’m not sure if your unit has this or the panel above the kitchen.

If you are using an On Board Diagnostic (OBD) reader, that means you are connecting to the engine diagnostics. That would have nothing to do with the house batteries. I would suspect the fuses you are checking are the automotive ones for the chassis.

Where to start testing batteries

I would start at the house batteries with a multimeter and check to see if they are at 12.6 volts. If not, they are your problem. You should be able to plug the unit into a shoreline power source that has at least 20 amps and the converter will kick in and try to charge the batteries. At this point you should see 13.6 volts even if the batteries are dead. That will provide power to the 12-volt components.

If you do not have power to the components, check your battery disconnect switch. That is typically located on the side of the entrance step inside the rig. This is like disconnecting the negative cable so there is no parasitic drain when you put the unit into storage. Here, again, is the 2003 Brave. You can see the switch on the left side hanging out, as we were replacing the carpet.

If this switch is in the off or “store” position, nothing powered by the 12-volt house batteries will operate. This is wired to a solenoid, typically in the compartment with the batteries, and that can also be bad or stuck in the off position.

Related:

RV ‘Gremlins’, Part 2: The mysteries of 12-volt wiring


Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

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