Two sets of power coming into bathroom lights.

[wildwest450]

Ok, I ordered a new bathroom vent with a fan and I was digging around for a way to route power to it. My one bathroom light has two white and two black power lines coming into the light, but nothing going out from it, very strange... The other light has only one set of wires, but it's next to impossible to tie into it.

Could it possibly wired for a fan and they just tied off into the light?
That would be sweet, I can find no other logical reason for the double wires.

[RedG]

SaltiDawg wrote:

wildwest450 wrote:
It doesn't make sense that it's part of a "string" because it's the farthest light away from all other lights. The wires definitely come from the direction of the fuse box, but continue no further than the light. The other bathroom light has a single wire that come in from another direction.

Farthest geographically may not mean farthest electrically. Separate the whites and separate the blacks and see if both whites are hot - if not, it would seem to indicate the connection is simply passing power thru in a chain.
I have zero RV knowledge or experience, I was just trying to suggest some possible help.

White wires are ground. The black wires should be hot.

[Bob_Landry]

RJsfishin wrote:
Quote:

ONE thing you need to so though is hang a meter on the wirs.. YOu may find the black lead is POSITIVE
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Really ? like that mite be a surprise ? Hmmmmmm, I thought in a B&W situation, black is always positive.

That's usually correct on trailers and white is used for ground. In the rest of the DC world, black is negative. One reason that ABYC adapted using yellow and/or brown wire for DC ground was that there were instances where unknowing owners trying to install their own equipment tied DC ground and AC hot, both black, together causing some really interesting problems.

[RJsfishin]

Quote:

ONE thing you need to so though is hang a meter on the wirs.. YOu may find the black lead is POSITIVE
-----------------------------------------------------------------------
Really ? like that mite be a surprise ? Hmmmmmm, I thought in a B&W situation, black is always positive.

[gon2dadawgs]

Turn all lights on and disconnect the wires.....one, or more, lights will go off...like many have said its part of a string.

Michael

[Dutch_12078]

That's terrific! I'm glad it worked out well for you...

Dutch

[wildwest450]

Update, the other set of wires did indeed go to the other light, even though the routing is all crazy. I contacted Fan-Tastic and they said it was no big deal to hook up a fan to a light circuit, everything went well and I have an awesome new fan. If you don't have a fan in your bathroom, put one in, it's worth any amount of trouble.

[wa8yxm]

Two pair of black and white wires.. Odds are one pair is the line to the other light... And you can tie in at either light, no problem.

ONE thing you need to so though is hang a meter on the wirs.. YOu may find the black lead is POSITIVE (After all, the folks who wired it up at the factory are NOT automotive/electronics types. they are house electricians and thus use color ... Differently than us electronics types)

[MEXICOWANDERER]

RV manufacturers use the cheapest way to junction wires they can get their mitts on. It may not look logical but some bean counter figured out your example is the cheapest way to power all the loads in the area.

[Bob_Landry]

12V lights on a string are always going to be wired in parallel, black or red is hot, white should always be ground. If there is no wall switch for the overhead light, then it is hot all the time and you are safe tying into them anywhere to power the fan.

[wildwest450]

Dutch_12078 wrote:
My bathroom has four wires at the light fixture in the shower, with one pair feeding power in, and the other pair continuing on to the vent fan. My old Class C had the same arrangement, but there was no fan installed. I found the wires for adding one when I removed the vent trim.

Good info, thanks.

[Dutch_12078]

My bathroom has four wires at the light fixture in the shower, with one pair feeding power in, and the other pair continuing on to the vent fan. My old Class C had the same arrangement, but there was no fan installed. I found the wires for adding one when I removed the vent trim.

[wildwest450]

Thanks for all the help, I forget that an rv isn't a house. I'll probably go buy a voltmeter and see what the deal is. I thougt it possible that all models were wired the same, and I would luck out on a fresh circuit for my fan.

[westend]

Yes, it should be fine to grab power for your fan from the light fixture. Hopefully, there is adequate 12v distribution so the bath light circuit is independent from other 12v draws. Best practice would have the lights on one branch circuit and other devices on a separate branch.

When you find four wires into a location, you can be 99% sure that it is part of a string. Direction of wire exits/entrances has little meaning in the RV world.

[SaltiDawg]

wildwest450 wrote:
It doesn't make sense that it's part of a "string" because it's the farthest light away from all other lights. The wires definitely come from the direction of the fuse box, but continue no further than the light. The other bathroom light has a single wire that come in from another direction.

Farthest geographically may not mean farthest electrically. Separate the whites and separate the blacks and see if both whites are hot - if not, it would seem to indicate the connection is simply passing power thru in a chain.
I have zero RV knowledge or experience, I was just trying to suggest some possible help.