Friday, September 17, 2021
Friday, September 17, 2021

Ask Dave: All our lights keep going out, but our appliances work! What gives?

Answers to questions about RV Repair and Maintenance from RV expert Dave Solberg, author of the RV Handbook and the managing editor of the RV Repair Club. This column appears Monday through Saturday in the RV Travel and RV Daily Tips newsletters. (Sign up for an email reminder for each new issue if you do not already receive one.) Today Dave discusses why an RV’s lights go out while appliances still work.

Dear Dave,
Over a week ago all the interior lights including the porch light, exhaust light and exhaust fan went off. Just when my husband seems to have found the problem the fuse blows out again. All the electrical outlets work and so does bringing in the steps, microwave and refrigerator. What can be causing this? He has looked and done everything possible. —Rosie

Dear Rosie,
There are two different electrical systems used in your RV: 120-volt AC and 12-volt DC. The 120-volt AC system is similar to your home and supplies power to the outlets, roof air conditioners, and any appliance that runs on 120-volt power. Typically, these appliances such as the microwave and refrigerator are plugged into a dedicated outlet rather than hard-wired directly. 120-volt power is supplied from an outside source such as the campground pedestal or a generator to the distribution center, which has circuit breakers for each application.

The 12-volt DC system utilizes deep cycle batteries to provide power to the interior lights, vent fan, and any appliance operating on the LP mode. The house batteries supply power through the distribution center with automotive-style fuses, which I assume you are referring to that have “blown.” So, you have an issue with something on the 12-volt DC side of the system, since the refrigerator and microwave are working.

How to troubleshoot why the lights go out

My guess is you have a light fixture that has a loose connection causing a short or a wire that has been compromised with either a cut or screw driven through. These can be hard to find as they can be intermittent. I would start by removing all bulbs in the light fixtures and reinstalling one by one to see if you can get the fuse to blow. That will identify the faulty light or even wire.

You may need to run a new dedicated wire from the battery to individual lights. This is a long process but is easier than trying to trace wires that are embedded into the sidewall or ceiling!

Typically, the exhaust fan is not on the same circuit as the lights and should have a dedicated fuse just for that. If it does and both the fan and light fuses are blowing, then you have a wire touching somewhere. Take a look at the fuse panel and identify each circuit and isolate what is actually blowing or not working.

Read more from Dave here

Dave Solberg worked at Winnebago for 15 years developing the dealer training program, as marketing manager, and conducting shows. As the owner of Passport Media Creations, Dave has developed several RV dealer training programs, the RV Safety Training program for The Recreation Vehicle Safety and Education Foundation, and the accredited RV Driving Safety program being conducted at rallies and shows around the country. Dave is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club.

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Susan C.
20 days ago

My interior ceiling lights stopped working and the fuse blew when I tried replacing it. A technician had replaced my bathroom exhaust fan just before this happened. I removed the fan and discovered he had not run the wires through the cutout provided on the fan housing; the wires were squashed between the housing and the wooden ceiling structure. I rerouted the wires in the proper groove, and the lighting problem was solved. Have any ham-handed techs been working on your rig recently?

Drew
20 days ago

Here’s a good instructional video that will help you locate a 12v short:

https://www.youtube.com/watch?v=m-rLnWqRMbs

Thomas D
20 days ago

What size fuse is blowing in amps.
What or how much current is it taking to blow?
Is the circuit overloaded?
Is it a short?
All important questions.
A digital multimeter set on amps could help.
Asking me or anyone else is like blowing in the wind. You need a meter and understanding to proceed.
I have a meter that reads current and traps the answer so you don’t miss the reading when it blows if you happened to look away at the wrong time.
You mentioned that the vent fan, porch light and ? blew the fuse. If you leave one or the other off does it blow?
So many questions!
Changing a wire? In the wall, ceiling.
BIG JOKE. let me know how that works for you!

David Telenko
20 days ago

I have been following https://rvelectricity.com/ with Mike Sokol & he & his moderators have helped hundreds if not thousands of troubled RV’s with their electrical issues & can be repaired by the average RVer, but some are more complicated & need a professional to do the repair.Check out his web site https://rvelectricity.com/
Snoopy

Bob S
20 days ago

It is important to understand exactly which lights and other fixtures and components are failed when the fuse if blown. Check you wiring diagrams, if available to get an idea of how they are wired together. Then use Mike Sokol’s ingenious technique to troubleshoot short circuits. He connects a 12 volt light bulb across the blown fuse contacts. The short circuit lights the bulb. Now you can trace the wiring from one fixture to the next. When you disturb the intermittent shorted wire, the light bulb will go out. Now you have isolated the short. A close inspection of the wiring should reveal the short.

Crowman
20 days ago
Reply to  Bob S

That’s a better answer than run a wire from the battery to the light.

TIM MCRAE
20 days ago
Reply to  Bob S

Great idea. Do you have a link to Mikes article?

Not sure what you mean by ‘across the blown fuse’. If you mean across the contacts (from one to the other) you are replacing the fuse with a light bulb filament. I think I would test for the current draw across the light bulb before proceeding to toubleshooting.

Admin
RV Staff (@rvstaff)
20 days ago
Reply to  TIM MCRAE

Hi, Tim. You can go to RVtravel.com and search for “Mike Sokol short circuits”. He has several articles on the subject. Have a great day. 🙂 –Diane

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