Looking for speculation/opinions on what might be going on here....It all started when the HW heater blew its fuse. I determined the cause and fixed it. Not having any spare fuses, I pulled a fuse from a spot marked "SPARE" in the panel. I suspected it wasn't really a spare because there was a red wire attached to the lug that disappeared into the wall. But, removing the fuse didn't really seem to affect anything - at least at first.So I'm replacing my toilet. Another long, boring story about a project that should take 15 minutes but is dragging on into days. But I digress. While working in the RV I noticed that the lights were flickering and eventually went out. Upon closer inspection, the lights that were "out" were very dimly lit - they were getting a tiny bit of power from somewhere. The other light circuit - powering the other half of the RV - was fine. I unplugged the shore power and plugged it back in and everything was fine again.Well, it did it again this morning so I thought about what might be different. That fuse. I yanked the fuse from the WH spot and touched it to the "SPARE" spot. All the lights turned back on. But get this - I didn't install the fuse - just touched the contacts momentarily. WTH? Because it was obvious that this fuse is of great importance to the balance of my lighting universe, I reinstalled it. But the question is - what is it powering that has this effect on just one lighting circuit?Ideas?

turbojimmy,My guess is that the dim lights indicate a poor ground connection in the lighting circuits. JM2¢...

Might go back to the batt and your converter wires are loose are dirty your not getting full voltage out of the converter

My guess is the "Spare" is not powering anything,,,,, it is ACCEPTING power from your converter.. Is it, per chance a 30 amp fuse?Oh, and the key word in the above is: GUESS

wa8yxm wrote:My guess is the "Spare" is not powering anything,,,,, it is ACCEPTING power from your converter.. Is it, per chance a 30 amp fuse?Oh, and the key word in the above is: GUESSIt's a 20-amp fuse at the top of the panel. But the weird thing is that if I touch the fuse to the contacts (not install it) the lights come back on. I haven't figured out what the trigger is for them going back out. And, the real mystery is that only one light circuit goes out. All other circuits remain powered. And by "out" they're not completely out - just really dim.It's an old-school fuse panel that looks a lot like the breaker panel in a house. Big black wires feed lugs that distribute the power to the fuse holders. There's a bar up the left side and the circuits are fed from the right side The red wire is definitely a "goes outta" not a "goes inna". It appears to have been added post-manufacture because all the other wires enter and exit through the ceiling. This one goes through the wall. I can't get to the other side of it because it goes between the closet and shower.The curiosity is killing me but I have bigger fish to fry currently. I discovered the issue while replacing my toilet and the bathroom light went out. Still in the middle of that job.

teddyu wrote:turbojimmy,My guess.... . . previous owner got into the electrical system (that spare fuse slot should not be wired). If you don't have a wiring diagram, draw one up. Check, clean, add dielectric grease to your connections in weather vulnerable areas, inspect batteries.Last resort, hire a good rv/automotive electrician to help. Mine retired long ago to Bora Bora after doing extensive (read expensive) work on my old Peterbilt.

Mysterious Electrical Issue | Good Sam Community

teddyu
Explorer
Jul 02, 2014
turbojimmy,

My guess is that the dim lights indicate a poor ground connection in the lighting circuits. JM2¢...
newman_fulltime
Explorer II
Jul 02, 2014
Might go back to the batt and your converter wires are loose are dirty your not getting full voltage out of the converter
wa8yxm
Explorer III
Jul 03, 2014
My guess is the "Spare" is not powering anything,,,,, it is ACCEPTING power from your converter.. Is it, per chance a 30 amp fuse?

Oh, and the key word in the above is: GUESS
turbojimmy
Explorer
Jul 03, 2014
wa8yxm wrote:
My guess is the "Spare" is not powering anything,,,,, it is ACCEPTING power from your converter.. Is it, per chance a 30 amp fuse?

Oh, and the key word in the above is: GUESS

It's a 20-amp fuse at the top of the panel. But the weird thing is that if I touch the fuse to the contacts (not install it) the lights come back on. I haven't figured out what the trigger is for them going back out. And, the real mystery is that only one light circuit goes out. All other circuits remain powered. And by "out" they're not completely out - just really dim.

It's an old-school fuse panel that looks a lot like the breaker panel in a house. Big black wires feed lugs that distribute the power to the fuse holders. There's a bar up the left side and the circuits are fed from the right side The red wire is definitely a "goes outta" not a "goes inna". It appears to have been added post-manufacture because all the other wires enter and exit through the ceiling. This one goes through the wall. I can't get to the other side of it because it goes between the closet and shower.

The curiosity is killing me but I have bigger fish to fry currently. I discovered the issue while replacing my toilet and the bathroom light went out. Still in the middle of that job.
Beosuun
Explorer
Jul 03, 2014
teddyu wrote:
turbojimmy,

My guess...

. . . previous owner got into the electrical system (that spare fuse slot should not be wired).

If you don't have a wiring diagram, draw one up. Check, clean, add dielectric grease to your connections in weather vulnerable areas, inspect batteries.

Last resort, hire a good rv/automotive electrician to help. Mine retired long ago to Bora Bora after doing extensive (read expensive) work on my old Peterbilt.
turbojimmy
Explorer
Jul 05, 2014
The plot thickens....

Went out there today and the mystery fuse is blown. No lights in the back. But that's not the circuit they're supposedly on.

The "spare" is hand-written on the box. I'm thinking it's not really a spare. But there are 2 circuits involved in illuminating those back lights for some reason.

I've had the rig since December of last year, plugged in pretty much continuously. Never had this problem. I'm thinking it's the shower fan. I recently replaced the motor and fan blade. But the fan blade spun the wrong way. I reversed polarity on the motor. But the switch is bad and runs at random. I'm thinking there's some resistance through the switch. Gonna clip the wires and see.

But I'm out of 20A fuses for now....
rgatijnet1
Explorer III
Jul 05, 2014
They make "circuit breakers" that can replace most 12 volt fuses that are great for trouble shooting. These are available at most auto parts stores. You can also use many hand held voltmeters to measure current/amps and attach it in the circuit, in place of the fuse, to see exactly how many amps are passing through that lighting circuit. Might help with the troubleshooting process.
Lobstah
Explorer
Jul 06, 2014
It seems like when you "touch" the fuse, you're setting/resetting a relay.

Jim
garry1p
Explorer
Jul 06, 2014
A guess here but take a look at the fan switch and see if you have 2 wires connected to the "motor side" of the switch or an extra wire at the motor.

What I'm thinking is the problem light is getting it's ground through the fan motor. That could explain the motor running at random as it is also getting 6V through the problem light when that switch is "on"

A test would be to turn on the problem light and check the fan to see if it running at half speed or even slower.

The logical explanation is the bulb is getting it's ground from an unknown source. Having said that many times electrical circuits do not behave in a logical manner.

Whatever the problem let us know when you get it worked out.
Fleetwood99
Explorer
Jul 06, 2014
turbojimmy wrote:
Looking for speculation/opinions on what might be going on here....

Battery Negative(-) Loose, dirty, corrosion of a common wire that supplys that branch of Lights is my guess.

Forum Discussion

Mysterious Electrical Issue

About Motorhome Group

Related Content

Electric issue

Electrical Issue

Mystery Electrical box under dash

Electrical issue

Electrical issues