Why does RV’s 12-volt fuse light show blown fuse but everything works?

Dear Dave, 
Looking at my 12-volt panel, I get a red light next to a fuse if it blows, which is very handy. However, I now have a situation where this red light is on for fuses that are good and the circuits they guard are working fine. So I don’t understand why this red light is on? —John, 2015 K-Z Spree travel trailer

Dear John,
The lights are on fuse block F7 and F11, so the first thing is to identify what component they go to. It could be deceiving as every LP appliance requires a 12-volt feed as well as the air conditioners and other items that seem to run on 120-volt power only. So the fuse might be blown or “open,” as indicated, but you might not realize what component it is going to and might not be using them. There should be a label on the side of the door that indicates what each fuse is for.

How to test a 12-volt fuse panel

When you identify what component they protect, pull the fuse to verify that component was working and stops when the fuse is pulled. I have found some of these have been mislabeled when installed or rewired.

Then use a multimeter to verify the fuse is actually good. Set it on the continuity setting and touch each of the terminals. You want to do this with the fuse out to make sure you do not create an issue with a live circuit.

You could also use a 12-volt test light to verify 12-volt power on the outgoing side of that circuit.

Next, try installing a new 15-amp fuse into the circuit and see if it still lights up.

If you verify the components protected by the fuse are receiving 12-volt power and working, then it most likely is a malfunction of the board the LED light is on. You could move the wire to an open slot on the board with a new fuse. If it works without the light, it is that slot/s. Loose wires or hairline cracks in solder can be real gremlins.

 You might also enjoy this from Dave 

Why does toaster oven trip the GFCI in RV bathroom?

Dear Dave,
I am new to this camper and although most things are going well, I had a problem when I tried to use a toaster oven in the kitchen. After turning it on and trying to make some toast, it ran for about 30 seconds and then turned off. My multimeter was not handy, but I soon realized that the bathroom GFCI had tripped. There were no other appliances in use at the time….

Read the rest of Mark’s question and Dave’s answer.

MORE POSTS FROM DAVE ON RV ELECTRICITY

• Powering your RV: Essential 120-volt electricity tips and gadgets for every RVer
• Why does an RV fridge work on LP but blow a fuse on electricity?
• Some fun facts I learned about electricity this week
• Follow-up on delayed converter charging and tripping GFCI issue

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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