Troubleshooting tail lights/bad ground - Fiberglass RV

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Old 08-22-2014, 12:25 AM   #1
Junior Member
Name: Manousos
Trailer: 1971 Boler 1300
British Columbia
Posts: 7
Troubleshooting tail lights/bad ground

Hi all,

I recently purchased a 15ft Beachcomber, and am in the process of trying to resolve an issue with the tail lights and running lights.

Basically, my tail lights and running lights only work (dimly) when I turn on the vehicle's headlights. When I use the turn signals all the trailer's lights (tail and running) flash dimly.

I had the same issue on an older trailer and was able to resolve it by fixing a loose ground wire, so I suspect the same applies here. So I just spent the afternoon checking all the lights and their grounds, some of the fixtures are old and the bulbs make poor contact in their sockets, but otherwise everything seems to be wired ok.

Is there a quick way to troubleshoot a possible bad ground?? I'm fairly comfortable with electrical stuff and have a decent multimeter

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Old 08-22-2014, 01:27 AM   #2
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Name: Dave
Trailer: Casita SD17 2006
Posts: 2,079
[QUOTE=manmade;478318]Hi all,

I recently purchased a 15ft Beachcomber, and am in the process of trying to resolve an issue with the tail lights and running lights.

When I first started reading your post....bad ground came to mind. But you have already looked into that. As all your lights seem to be affected I would lean more to the main ground. It could be the tug or the trailer with the problem. Some trailers ground through the ball, not the best. Using one battery jumper cable between the two would show if that is the problem. Don't ask how I know that and it's a quick easy check. If that didn't show any difference I would start checking all the connections from the plug to the trailer. Being your getting some light from everything the connection is there but something is loose or has corroded enough to not to give you a 100% circuit.
Rereading your post it reminds me of the differences to wiring the plug to the tug. When I went to pickup my Casita I had a round 6 pin on my truck. I made up an adapter from 6 to 7 pin for the trip home. After hooking up I had all the outside lights flashing too with the turn signals on but they were bright, OK, ground was good but...I disconnected everything in the adapter plug except the ground and with my wifes help tested each wire in different points until I had the lights working. There are two different wiring configurations, Bargman is one and I can't think of the other name now but they don't interchange. Good luck to you but do the jumper cable first as it's a quick test.

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Old 08-22-2014, 05:58 AM   #3
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mszabo's Avatar
Name: Mike & Sara
Trailer: 86 17' Bigfoot
Posts: 550
Let me see 43 year old wiring? Might be time to update!
Sometimes it's easier just to replace it.
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Old 08-22-2014, 06:05 AM   #4
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Jared J's Avatar
Name: Jared
Trailer: 1984 19' scamp
Posts: 1,610
Run a jumper wire from the tow vehicle ground cable to the ground for the light. If it gets brighter, you know you are chasing a ground. If you happen to be doing it hitched up, unhitch it. If a ground breaks completely, it will sometimes ground through the trailer ball and coupler, with all sorts of weird issues.

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Old 08-22-2014, 07:23 AM   #5
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Rick Mooyman's Avatar
Name: Rick
Trailer: 1971 Boler 13' / 2013 Ford Escape
Posts: 906
Just go to Princess Auto and buy a new wire harness and all LED light and be done with it. The old lights will be corroded too bad after all these years anyway and the LED lights will be brighter and you will be seen on the road much better. Also while you are at it you may as well put a high mount brake light on the trailer as well.
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Old 08-22-2014, 08:54 AM   #6
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Name: Carol
Trailer: 22' Airstream Formerly 16' Scamp
British Columbia
Posts: 11,706
I would also check for corrosion on the tugs plug/connection side - including where the wires go into the back of the connection. Corrosion on the wire connections both tug and trailer side can create all sorts of weird and not so wonderful electrical issues.
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Old 08-22-2014, 12:37 PM   #7
Junior Member
Name: Manousos
Trailer: 1971 Boler 1300
British Columbia
Posts: 7
Thanks everyone for the responses, will check with a jumper cable. Plugs are both new and corrosion-free
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Old 08-22-2014, 01:31 PM   #8
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Name: Steve
Trailer: Scamp 13
Posts: 1,036
If your tug uses a light converter allot of trailer wiring goes from the converter to a flat four plug. the the flat four plug plugs into or attaches to the 7 pin socket wiring. This flat four connector can give issues. Check the voltage coming out of the converter and also out of the 7 pin socket for each connection. If you have over 12 volts coming out from the tug your good to go.

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