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Soyboy · 06-29-2016, 09:21 AM

I'm replacing a rear marker light on my '99 Safari. It has 2 wires coming through the body/grommet (BTW, thanks for making the wires so short Airstream

). Both of the wires run into the actual light fixture. Anyway, the light seems to be grounded to the body by the attachment screws. If so, why are there 2 wires?

One might assume that one is hot and the other is ground however they both have continuity. So does that mean they are both hot? In another thread, someone suggested (but with no clear answer/reply) that these wires might be daisy chained to run the other marker lights. Maybe so, but why would they still have continuity when they are not attached to each other (one coming from the source and the other to the lights?

Any tips for figuring out if they are both meant to be hot, with one wire coming from the source and the other running to the next light? Or if one is ground, which one is it? I am kind of leaning towards them both meaning to be hot, as there is really no need for a separate ground wire with the metal body (at leaset that's what I would assume).

Thanks

TG Twinkie · 06-29-2016, 09:32 AM

You are reading thru the filaments of the other bulbs in the string. Were the 2 wires connected when you removed the old marker light? What color are the wires?

Soyboy · 06-29-2016, 09:42 AM

Thanks TG. They are both black.

If one is ground, why in the world didn't AS use a green wire? With red or black for hot. Sure would make life a lot simpler LOL.

Soyboy · 06-29-2016, 10:44 AM

After thinking about it, I jumped the umbilical so that the lights were on. That way I was able to determine the hot from the ground.

NevadaGeo · 06-29-2016, 12:03 PM

You may have to take all the bulbs out for a test. Some systems might not rely on the shell to be grounded.

mandolindave · 06-29-2016, 12:09 PM

It could be that both wires or hot. ( especially since both are black )

The ground on mine is to chassis. There is no ground wire. the mounting screw is the ground. The markers maybe daisy chained, one of the wires is positive, the other goes to the next light.

The reason why one wire seems to be not hot could be that you disconnected it from the circuit

Soyboy · 06-29-2016, 01:05 PM

Hmmm. Ok. I have a wiring schematic now that I think of it. I'll check that. If that doesn't help, I'll pull bulbs from the marker lights on either side of it in the circuit.

Thanks

woodfox45 · 06-29-2016, 01:24 PM

If they are both black it doesn't matter

HowieE · 06-29-2016, 02:35 PM

You have found that one wire is positive already. With power going to that wire put a light bulb between that wire and the other wire. If the bulb lights with normal brightness that second wire is a ground. If the bulb lights with a dim light and the other marker lights come on dimly the light are wired daisy chain. If the second case remove the bulb and touch the wires together. The other marker lights should light with normal brightness. Don't try this first because if that wire is a ground you will blow a fuse or melt the wire.

m.hony · 06-29-2016, 03:37 PM

I am thinking one wire is power to the light.
I am thinking the second wire is power to the rest of the light bulbs in the string/chain?

mayco · 06-29-2016, 04:28 PM

Harbor Freight is giving away a multi-tester with any purchase right now.

Soyboy · 06-29-2016, 04:33 PM

Thanks for all of your input (and any other is welcome). I'm going to hit is again tomorrow. I starting to think that they are "series" wires like some of you had suggested. I"ll see. I need to stock up on fuses!

I was also busy today carting my old wheels/tires to Costco to have my new tires mounted (Maxxis M8008s - my third set, I have had good luck with them so far....knocking on wood) Using ramps I took them up two at a time.

I'm also working on a dead outlet inside the trailer (the front outlet by the converter - I'm thinking the on-off switch might be intermittent). Man those RV outlets are crappy. Lots of fun. Maybe I'll trade it in on another Jayco. Oh nevermind, I had delamination with my last one LOL.....

I'm glad I'm retired and have time to mess with this stuff. I figure I saving that $100/hr + labor rate. Although it takes me 5 times as long as it would a knowledgeable mechanic).

Soyboy · 06-29-2016, 04:34 PM

Thanks Mayco, I have a couple including a nice Fluke.

mayco · 06-29-2016, 05:24 PM

Cant you use your tester to test each to ground? Then see if any other lights are working or not to determine if indeed the second wire feeds the the others? Test each to ground and test between the two to see if the second is ground or not. Mine are single wire and grounded to frame so didnt have that problem but thats how I would approach it. Maybe I dont understand, thats always a good posibility.

TG Twinkie · 06-29-2016, 05:50 PM

The lights are not in series. They are wired in parallel. Daisy chained just means they are all on the same circuit.

mayco · 06-29-2016, 05:54 PM

There ya go

Burnside Bob · 06-29-2016, 06:41 PM

Quote:

Originally Posted by Soyboy

I'm replacing a rear marker light on my '99 Safari. It has 2 wires coming through the body/grommet (BTW, thanks for making the wires so short Airstream

). Both of the wires run into the actual light fixture. Anyway, the light seems to be grounded to the body by the attachment screws. If so, why are there 2 wires?

One might assume that one is hot and the other is ground however they both have continuity. So does that mean they are both hot? In another thread, someone suggested (but with no clear answer/reply) that these wires might be daisy chained to run the other marker lights. Maybe so, but why would they still have continuity when they are not attached to each other (one coming from the source and the other to the lights?

Any tips for figuring out if they are both meant to be hot, with one wire coming from the source and the other running to the next light? Or if one is ground, which one is it? I am kind of leaning towards them both meaning to be hot, as there is really no need for a separate ground wire with the metal body (at leaset that's what I would assume).

Thanks

My experience may prove useful. I removed and replaced all of the marker lights in my 2009 Flying Cloud. I also replaced the wiring in the top of my trailer by removing the interior ceiling panel.

All of my clearance lights were wired with dedicated hot (green) and ground (white) 10 gauge wires, i.e. "wired in parallel". It was because they were wired with 10 gauge wire that the connectors could not be pulled thru the grommet from outside the trailer--the connectors were too fat to fit thru the grommet.

In this day and age, it is unlikely that anyone's marker lights are wired in series, also called "daisy chaining", because failure of one bulb would mean all marker lights in the series (daisy chain) would go out.

If both marker light wires are the same color, it does not matter which is connected to hot and which to ground.

Hope this helps.

TG Twinkie · 06-29-2016, 07:21 PM

I believe the OP. is referring to the wires coming out of the coach. Not the fixture. IMHO neither should be grounded. They should be connected to the marker light. If the marker light only has 1 wire that is the +12 volt side. The marker light then has a grommet at one of the mounting holes which will complete the circuit when mounted to the skin.
If there are 2 wires in the light fixture they are as follows.
If red and black; red is + black is -
If black and white; black is + white is -

PeterH-350LE · 06-29-2016, 07:31 PM

Quote:

Originally Posted by TG Twinkie

I believe the OP. is referring to the wires coming out of the coach. Not the fixture. IMHO neither should be grounded. They should be connected to the marker light. If the marker light only has 1 wire that is the +12 volt side. The marker light then has a grommet at one of the mounting holes which will complete the circuit when mounted to the skin.
If there are 2 wires in the light fixture they are as follows.
If red and black; red is + black is -
If black and white; black is + white is -

on my 1997 Excella trailer they both were black. One was 12V and the other ground. Even with all the marker lights disconnected, you can not measure resistance. The tail light are in the circuit and will give wrong reading, since they are incandescent.
Best way is to jump 11 and 1 o'clock on the plug with a blade fuse and then measure which is 12v

Soyboy · 06-29-2016, 08:10 PM

Peter:

Thanks, I did that today and one did show 12V and the other zero. I wish I had taken notice if the other marker lights along the top were on, seems stupid, but I was so intent on measuring for voltage that I didn't notice. DUH. Since our trailers (Peter) are of the same vintage I guess then one is hot and the other ground even though Airstream had two black wires coming through the grommet to the light. I also busted into the old light fixture and I could see that one wire went to one side and the other wire to the other side, which should show that one is hot and one is ground. I'll find out for sure tomorrow, one way or the other LOL.

BTW I mentioned schematics earlier, turns out I had one for everything EXCEPT THE EXTERIOR LIGHTING. ROFLMAO.

I'll let you guys know how I make out. I really appreciate all of the input!

Trying to get things in place so we can head to the beach next week and I can watch my polished exterior corrode in front of my eyes

Oh well, that is what a Cyclo is for.

Den