Monday, December 5, 2022


Ask Dave: Why don’t the RV’s bath area lights and fan work?


Dear Dave,
All the lights work in the camper except in the bathroom area. No lights in the bathroom, the hallway or the vanity, and no bathroom fan. I have checked all the fuses. Thank you! —Michael, 2007 CrossRoads Cruiser

Dear Michael,
I would start at the distribution center, where you have the 120-volt circuit breakers. There should be a row of automotive-type plug-in fuses that are for the 12-volt system. Verify what 12-volt fuses you have for the bathroom area. Typically the fan is on a separate fuse from the lights, but I have seen stranger things.

This is a typical distribution center. You should be able to find the fuses for the lights and fan and verify the fuse is not blown. Typically the color-coded wires will then come off the fuse out the back and run inside the cabinet or wall up to the ceiling. However, every manufacturer does things differently, so sometimes wires are run differently from one model to the next.

If the fuses are good and you have 12-volt power coming in and going out, there must be an open condition in the wiring going to the bathroom. Make sure the unit is unplugged and the negative cable is disconnected from the house battery. Then pull out the distribution center slightly to find the wire dedicated to the lights and fan. It might be color-coded or even stamped with a code, but most of the trailers are not.

Find where the wiring goes

See if you can find if the wiring goes up to the ceiling or down and underneath through a compartment. If you are lucky, you might find the wiring hidden in a wall or cabinet directly behind it. See if it goes to a junction box, then to the bathroom. My guess is either one or more wires goes to the bathroom area and then is “ganged” to the other lights. So, if there is an open circuit, none of them will work. This could be caused by a screw run through the wire, or a loose connection at the first fixture.

The next thing I would check is the ground. These fixtures could be grounded to a piece of framework close to the bathroom that had developed a crack and no longer provides a ground. New manufacturing typically has the ground wire going back to the negative bus bar at the distribution center. Sometimes I just run a new ground “test” wire to the appliance or fixture to verify it is not the ground.

Next, I would check continuity from the distribution panel to the fan first by getting a long piece of wire and a multimeter and hook the wire to the fan positive wire and check at the distribution center fuse.

CrossRoads is made by Thor, and a technician I talked to said they have generic wiring diagrams but need the floor plan.

 You might also enjoy this from Dave 

RV “Gremlins”, Part 2: The mysteries of 12-volt wiring

I don’t know if I can actually say what “Gremlin” frustrates me the most. However, 12-volt DC wiring has to be up there with the worst of them!

Continue reading.

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

Read more from Dave here


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Ron Seidl P.E.
4 months ago

I would also check the wiring connections in the light nearest the bathroom. The bathroom lights may come from the nearest light and it may have a loose or broken wire.

4 months ago

Definitely check and tighten all connections in and behind your power center. The original owner of my trailer had no overhead lights when it was delivered new. Delivery driver shrugged and said sign here. He chased it down to loose connections at the ground buss bar behind the power center. Since then I have also retightened all connections. Good luck.

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