I've got a 12-volt light above the passenger seat that does not have a good ground. The positive side of the light is getting good voltage and it works when I manually ground it. I removed the light and the negative is no good coming to the fixture. I pulled the bottom out of that cabinet thinking the problem was there and it would be an easy fix. As my luck would have it, the wire disappears into an inaccessible cabinet toward the front AND there is NO other ground in there to tie the fixture. I do have easy access to a 120-volt plug. Is there a problem of supplying the 12 volt light fixture from the ground of the 120-volt plug? I know it will work but would there be any negative effects to permanently wiring it like that. I really don't want to start tearing out cabinets.

the ground end will be at the converter panal it might just need tightened up

newman fulltimer wrote:the ground end will be at the converter panal it might just need tightened upIs the converter panel on the converter or where might it be? All other lights and the 12-volt system works everywhere else. I wouldn't think there would be a wire for just that one light. There are probably 150 or more white wires all over the coach so that one might be hard to trace since it disappears into a cabinet. My coach is a 2002 Monaco Windsor.

I would Not connect those two grounds together. For 12 volt ground I would use the chassis if you can not find the ground wire.

Mandalay Parr wrote:I would Not connect those two grounds together. For 12 volt ground I would use the chassis if you can not find the ground wire.That would be my preference.

Mandalay's opinion is what I'd do.

12 volt to 120 volt ground | Good Sam Community

21 Replies

wolfe10
Explorer
Sep 22, 2017
Were it me, I would just use a magnet to locate the nearest chassis member and run a new ground wire to it. Should be one within a foot or two.
Sparksvonrou
Explorer
Sep 22, 2017
I would think that wisdom would suggest never connecting any DC connection to any AC connection ever. Mainly because though it would work, what happens when someone (or in my case me) later forgets what was connected where and thinks it something to do with AC or shore power.
Hank_MI
Explorer
Sep 22, 2017
As mentioned previously, multiple times, the 120VAC ground is connected to the chassis. The 12VDC negative(ground), from both the chassis and coach batteries are also connected to the chassis. So obviously both systems share a common ground.

wa8yxm wrote:
...The 120 volt ground often sits at 60 VAC believe it or not (I can explain why but it's not important).

Not important, oh it's definitely important. It's both wrong and hazardous. I wouldn't want to stand on damp ground and touch your chassis, 60VAC will give you a good tingle. Bare feet and could be deadly. If the chassis ground is floating at 60VAC then there is most likely a fault in supply wiring.

I have seen this situation before and got a shock from the screen door. It was due to mis-wired supply.
midnightsadie
Explorer II
Sep 22, 2017
its ok we all have those senior moments.glad you woke up before you tore things apart.
wa8yxm
Explorer III
Sep 22, 2017
What the other poster improperly called "The converter panel" is in fact the Fuse box. the panel with the 12 volt fuses on it. there may or may not be a converter there, the proper name is 12 volt distribution panel but we normally just call it the fuse block, panel or box.

I agree with the "I would not tie to the 120 volt ground" you could end up in a very bad way doing that. The 120 volt ground often sits at 60 VAC believe it or not (I can explain why but it's not important).

Better to find a chassis ground spot if you have to.
Tinstar
Explorer
Sep 22, 2017
dougrainer wrote:
There are some smart people on these forums. But to think sharing a GROUND between the systems would ever cause a problem is just crazy. Especially a VERY low volt draw from a map light. Doug

As I understand they are tied together anyway. Where seem irrelevant. Thanks for your insight Doug.
dougrainer
Nomad
Sep 22, 2017
There are some smart people on these forums. But to think sharing a GROUND between the systems would ever cause a problem is just crazy. Especially a VERY low volt draw from a map light. Doug
darsben1
Explorer
Sep 22, 2017
You may have looked dumb but it did not cost you anything.
time2roll
Nomad
Sep 22, 2017
You don't need to follow the ground through the cabinet inch by inch. Wire is probably fine. You just need to find the other end and fix the connection.

No, I would not share with the 120v fixture.
Tinstar
Explorer
Sep 22, 2017
Well, it's a mute point now. As always dougrainer was right,,, AS USUAL. I checked my dash switches, drivers side panel switches and nothing. I happen to think there are 3 switches beside her arm rest and one is labeled "MAP LIGHT". Surprise, suprise, I flip it and the light comes on. DUH, my DW said the light used to work but I didn't listen or didn't ask how she turns it on. In my defense, that light is the only thing controlled by the switch. My map light works by flipping the switch on the fixture.

That's what I get for thinking; I know what I'm doing. Lesson learned,,, until the next time I do something dumb. It wasn't bad taking the fixture and bottom of that cabinet out then putting it back together but it was a lot more trouble than it should have been.