No ground to three DC light fixtures.

Hello my name is Circe,

We own a 2002 Monaco Dynasty motorhome, and to make a long story short.  We have lost the ground to three sets of DC lights, on two different slides.  We discovered this when the light fixture over the sink burned out, and after determining it wasn't the tubes or the fuse, my husband removed the fixture and discovered that the underside of the fixture was badly burned.  As the fuse tested good, his search began and he discovered the loss of the ground to the kitchen light and two other lights one of which is on a different slide. 

We were experiencing difficulties with the GFI plug in the bathroom, and it ultimately reached the point where we could no longer get it to reset.  When it would blow, it would knock out the AC system, but the DC system remained in working order.  Logic told us that a GFI was not necessary for a motorhome because all the plumbing was plastic.  As my husband had a standard outlet available he installed that and we no longer lost our AC side of the system.  As we have been searching for the problem to the 3 DC light fixtures, we both began to wonder if somehow the AC and DC systems are somehow connected through the GFI outlet.  Keep in mind, we are grabbing at straws here. 

We purchased this coach as the second owners, and until this problem, we've had no difficulty.  We didn't receive and owner's manual or an electrical schematic, but my husband was able to download the owner's manual but it did not contain an electrical schematic.  In our search of the web for a schematic, all the sites, have asked the kinds of questions which suggest someone is trying to sell us a new coach. 

BOTTOM LINE, HELP!!!!!!

First, welcome to the forum
The AC and DC together have nothing to do with that GFCI. And by Code, you need that GFCI. Purchase a new one and install it. It is there to protect you and your love one's when you are near water like in the kitchen and bathroom sinks and the outside outlet.  The AC IMO would have nothing to do with that GFCI. The AC will be on it's own circuit breaker.

Thank you for your reply, and yes we know it is code...  and as I had mentioned, we were grasping at straws.  My husband is trying to figure out how he can restore the ground to those three fixtures. 

you can hunt for a ground point ....by connecting the alligator clamp of a cheap harbor freight 12vt test light to an energized positive point on the light fixture,  then take the pointed probe and poke around on the metal parts in the slide, when or if you hit a ground point it will light up.

then you can use another piece of wire to splice into the bad ground wire and attach it to ground.  That may light up all 3 fixtures.

good luck

Circe said:

Thank you for your reply, and yes we know it is code...  and as I had mentioned, we were grasping at straws.  My husband is trying to figure out how he can restore the ground to those three fixtures.

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Did these lights ever work?

Logic told us that a GFI was not necessary for a motorhome because all the plumbing was plastic.

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Those two things are unrelated. The reason for having a GFCI has nothing to do with plumbing. Your motorhome has an extensive metal chassis and probably a fair amount of metal in the body structure as well, any of which serves as a lovely electrical path in the event of a short. So do your fingers, if a fixture or appliance happens to short to its case or frame. Like dropping a hairdryer into a sink of water, or a heating element that breaks and touches surrounding metal.

The "ground" that a ground fault detector is working on has nothing to do with the "ground" of a DC lighting circuit. "Ground" in this case means two entirely different things. A DC "ground" is merely the negative terminal side of the circuit, i.e. the return path for electricity to get back to the battery. Your lighting has an "open circuit", i.e power arrives on one side but can't leave on the other, so no current flows and the light doesn't work.