I have a short somewhere? How do I find it?

[JimMartin]

Just installed a new roof on my 1999 Coachmen Mirada. Problem is that I must have pinched a wire somewhere? 12v Ceiling lights in my RV don't work now. Checked the fuse, it was blown, replaced it and it blew as I plugged it in. Removed all the light fixtures from the ceiling, unplugged them all from there 12v wiring. So now nothing should be powered up my that circuit right? Tried to put a new fuse in but it blew right away?

How can I find this break in the wiring? Do they sell a tracer of some sort that can test the wires and find a break? :?

[MrWizard]

Thanks for the update
Good news is always nice
Glad you got it fixed

[JimMartin]

Update:

My idea of jumping the light wire from the good ceiling lights to the bad ceiling light won't work. I originally thought that just three of my living area ceiling light were affected by this short. But not the case. After digging back into it again today, I found out that this short affects three ceiling light, my exterior porch light, and my 12v TV antenna booster for my JACKS antenna.

So I decided to trace all the wires that are bad. Removed my Kitchen area upper cabinets and found the wiring harness for the living area. Five wire coming from the rear of the coach, and then branching off in different locations. I cut all the wires in the harness in two. Starting checking each wire one by one with a hot wire that I ran directly from the fuse box. BINGO!!!! I second wire I jumped blew the fuse. THIS IS THE BAD ONE!!! Fortunately this wire branched off to the just one ceiling light. So I then bypassed that wire and ran a new wire from the harness to that light. Then butt connected all the other wires back together and everything is working great again!!!

I guess I just got lucky on this one! Thanks for all the input.

[BTPO1]

It appears that you have already drilled holes to pull a new wire through. I have on occasion attached by soldering a new wire to the old wire and with the help of a helper pulled a new wire into the old run. It does not always work, but sometimes it does. I do have a lot of patience though since I don't like seeing wires outside of a wall and will spend days running wire in walls to keep them hid. JMO

[CA_Traveler]

OK, Didn't realize that you had isolated the short.

[JimMartin]

The new 3/8" plywood roof is put down with about 100 screws. Apparently one of those 100 plus screws has hit a wire. Unfortunately I can't back any of those screws out because the new rubber TPO roof is glued down and covering them all.

As far as the screws that hold all the 14" x 14" vents down, I will try and back them all out and see if that solves my problem.

What I mean by "wire disconnected from the fuse panel it disconnects the bad wire, which will eliminate the short" is that I'm no longer going to use that wire that goes from the fuse panel to the light. I will by pass it altogether.

[MrWizard]

your missing the point
did you screw down new underlayment (luan/plywood) before the TPO
IF not then the screw involved is one of the roof attachments vents, pipes, antenna.. etc.. or trim screw on the side
it is NO big deal to remove a couple of those screws
put sealant in hole and replace with shorter screw

just a matter of finding the bad one, by continuity testing while removing a few screws in selected spots

JimMartin wrote:
As far as removing the screw in the roof. That's not going to happen. New TPO roofing is all glue down.

I have unscrewed the wire were it goes into the fuse panel for now. There are only the four overhead double lights in the living area on this fuse. All the other ceiling lights in the RV are fine.

I decided to run a wire from the ceiling light in the hallway to the living area light. Going to try and do this by drilling thru the Styrofoam with a 24" long 3/8" drill bit, and then running a coat hanger thru it to feed the wires. Wish me luck!!

Do you think the fuse for the hallway ceiling light can handle 4 additional lights on it?

[CA_Traveler]

JimMartin wrote:
With the wire disconnected from the fuse panel it disconnects the bad wire, which will eliminate the short

Maybe I missed something: Removing the wire from the fuse removes the short from the fuse. But the short still exists in the wiring and will blow the fuse in the new circuit.

Have you tried connecting the lights to the new circuit with a temporary jumper?

[JimMartin]

Bumpyroad wrote:

JimMartin wrote:


Do you think the fuse for the hallway ceiling light can handle 4 additional lights on it?

put in LEDs if you are worried.
bumpy

Good idea!;)

[JimMartin]

CA Traveler wrote:

JimMartin wrote:
Going to try and do this by drilling thru the Styrofoam with a 24" long 3/8" drill bit, and then running a coat hanger thru it to feed the wires. Wish me luck!!

Do you think the fuse for the hallway ceiling light can handle 4 additional lights on it?

I'd first try a 1/8" fiberglass wire puller.

As for the fuse - maybe.

But how does this eliminate the short?

With the wire disconnected from the fuse panel it disconnects the bad wire, which will eliminate the short

[Bumpyroad]

JimMartin wrote:


Do you think the fuse for the hallway ceiling light can handle 4 additional lights on it?

put in LEDs if you are worried.
bumpy

[CA_Traveler]

JimMartin wrote:
Going to try and do this by drilling thru the Styrofoam with a 24" long 3/8" drill bit, and then running a coat hanger thru it to feed the wires. Wish me luck!!

Do you think the fuse for the hallway ceiling light can handle 4 additional lights on it?

I'd first try a 1/8" fiberglass wire puller.

As for the fuse - maybe.

But how does this eliminate the short?

[JimMartin]

[JimMartin]

[JimMartin]

As far as removing the screw in the roof. That's not going to happen. New TPO roofing is all glue down.

I have unscrewed the wire were it goes into the fuse panel for now. There are only the four overhead double lights in the living area on this fuse. All the other ceiling lights in the RV are fine.

I decided to run a wire from the ceiling light in the hallway to the living area light. Going to try and do this by drilling thru the Styrofoam with a 24" long 3/8" drill bit, and then running a coat hanger thru it to feed the wires. Wish me luck!!

Do you think the fuse for the hallway ceiling light can handle 4 additional lights on it?