Junction Box to Allow Re-Wiring Camper Trailer Lights

Question:

Right tail light and brake light will not work on our pop up camper. To eliminate a circuit issue, I wired in a new brown wire into the 7 pin plug and ran that back to the tail light. I also ran a new ground wire to the light fixture. Using a test light I made the following test: 1 test the new brown wire with the new wire runs- turn signal works. 2 hook up the new brown wire to the light fixture, hook up the new ground to the light fixture and test the actual contact point in the light fixture - turf signal works. It only seems logical that now I should be able to put in a new 2157 bulb and the thing should work, but it does not. Ive tried new bulbs, even moved the one from the left side over to the right, but it wont work. Im at a loss on this one. Any help would be appreciated. If pictures or video would be helpful just let me know. Thanks

asked by: Jon B

Expert Reply:

In your camper's 7-way wiring the tail light circuit is separate from the brake light circuit. Each is carried on different pins/wires in the 7-way. If you refer to the linked image you'll see the function-to-pin assignments for a trailer-side 7-way plug.

What they have in common is their ground and this is what I suspect is the issue. Some lights will used a wired ground while others will use the lights mounting hardware to make the ground connection. If I correctly understand the testing you've done you have confirmed signals are present at the bulb socket after you ran the new wires. With signals at the bulb socket and a correct functioning bulb installed I cannot explain why the light does not work unless there is an intermittent connection/short.

To save you a lot of time and hassle I recommend you install a junction box and new 7-way plug like # HS381-9000 on the trailer and make new wiring connections to each of the lights. The junction box gives you a handy protected place to make your wiring connections from both ends, from both the included 7-way trailer cord and the various lights on the trailer.

expert reply by: Adam R