Wacky light

[Barb and Alan]

We have a 1985 Bigfoot 175G with an electrical issue. All driving (running, tail, brake, and signal lights) work EXCEPT the right tail, brake, and signal. Any time power is on to the trailer, the dual filament bulb (tail, brake/signal) glows with a vengeance (see 13.5 volts below). I checked the ground and there's continuity between the left and right grounds and the left light works fine. When I energize the brake/signal by hooking the battery with jumpers to the trailer's pigtail I get 12.65 volts at that side of the socket and likewise in the other pin when I energize the tail light. Now for the weird. A voltage reading across the 2 positive socket pins yields 13.5 volts, even with the ground wire severed. I know, dead short, right? No burning smells, or damage evidence in the fuse panel, the converter, all connections seem tight. I just can't seem to locate the problem so hoping someone has seen this before.

I assume that since with just the battery turned on the one bulb burns very bright it would seem power for the driving lights does pass through the power center.

It worked fine last season, and the trailer was plugged in and heated all winter. There's no evidence of mouse activity, either.

Thanks in advance,

Alan and Barb

[Elizabeth EWA]

It sounds like the ground side of the socket is connected like it should be but there's a short from power to one of the two positive pins. My suspicion would be it's in the connector that plugs into the vehicle

Most likely it's the right turn signal wire that's shorted to the power.

[Barb and Alan]

Thanks. I was wondering if the connector and/or pigtail could be the culprit. I'll look into that next.

[John in Michigan]

- On the camper, are you using a standalone test battery at the 7 blade connector? If so, is there also a separate permanently installed battery on the camper?
- Have any wiring changes been made to the camper?
- Are you saying that the right tail light is always on when camper shore power or battery power is on? Its possible the left tail light brake/turn wire (brown) was inadvertently connected to camper power (black wire).
- Is the tow vehicle disconnected for all of the symptoms? If so, that would rule out wiring problems on the tow vehicle 7 blade connector and the tow vehicle in general.

[Barb and Alan]

Hey, John.

I should have mentioned that we've owned the trailer for 2 1/2 years and the problem started this winter when I noticed a red glow coming from under the cover. Fortunately I had an LED bulb in so the heat buildup was minimal. The problem exists whether a standard or LED build is installed.

I'm using the trailer's house battery, still connected to the trailer.

No wiring changes I'm aware of other than the installation of a solar system done several years before we purchased it.

Yes, the right tail/brake-turn bulb is always on when on shore power or battery power is on. No wiring changes or pigtail replacements yet, but there could be a fault in the connector or cable. The connector is next on my agenda to replace. Unfortunately to replace the pigtail involves some interior cabinet removal which I hope to avoid.

The tow vehicle is disconnected. When connected, the dual filament bulb doesn't light on any function.

Thanks for your thoughts.

[steve dunham]

Originally Posted by Elizabeth EWA

It sounds like the ground side of the socket is connected like it should be but there's a short from power to one of the two positive pins. My suspicion would be it's in the connector that plugs into the vehicle

Most likely it's the right turn signal wire that's shorted to the power.

I have to agree with Elizabeth . The brake , turn , running lights on your trailer are powered from the vehicle battery not from your converter or trailer battery . I would suggest that there is a high resistance unintentional connection in your 7 pin trailer cord cap .
Disconnect your trailer from your vehicle and see if the brake /turn signal light goes out . If the light stays on then disconnect the trailer battery and your trailer from shore power if the light goes out then I would check the 7 pin cord cap.
We had a similar issue after making a winter trip . Salt and crud got into the 7 pin connector and caused the 12VDC power to jump over to another pin on the 7 pin connector.

[John in Michigan]

Yep agree with Elizabeth and Steve. Start by checking the 7 blade connector on the camper...

[Barb and Alan]

Shazam, bazinga, and oh happy daze! I cut the plug off and got continuity between the black and brown wires. I installed a new plug and we're camping this weekend! Thanks to Elizabeth, Steve, and John for your time and experience.

[steve dunham]

Originally Posted by Deadhead517

Shazam, bazinga, and oh happy daze! I cut the plug off and got continuity between the black and brown wires. I installed a new plug and we're camping this weekend! Thanks to Elizabeth, Steve, and John for your time and experience.

Elizabeth deserves the credit ! I just followed her lead.
Glad it's solved so you can hit the road this weekend.
Have fun
We've got temps in the 20's and possible snow in our forecast so still waiting to dewinterize our trailer . Spring is just around the corner ??

[Barb and Alan]

Originally Posted by steve dunham

Elizabeth deserves the credit ! I just followed her lead.
Glad it's solved so you can hit the road this weekend.
Have fun
We've got temps in the 20's and possible snow in our forecast so still waiting to dewinterize our trailer . Spring is just around the corner ??

Man I hope so! Here in the Pacific Nortwet it's been rainy but warming. And if you won't get out in the rain, you'll never get out.