Left Tail Light on Trailer With 5 Wiring Harness is Not Working Properly

Updated 03/17/2017 | Published 03/16/2017

Products Featured in This Question

Hook Probe Circuit Tester

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$13.47

Deka Heat Shrink Butt Connector - 16-14 Gauge - Nylon Insulation - Blue - Qty 10

(1188)

$17.19

14 Gauge Primary Wire - Black - per Foot

(51)

$0.83

Question:

Just cleaned up a bad ground on left taillight. Now I dont get it. Signal/brake light only comes on with running lights. Is there a short? Why do I have four wires white yellow brown black. Two bulbs in light.

asked by: Derek S

Expert Reply:

From your picture and your description, I would say that your left turn, tail, and back up signals are all run on separate wires instead of being combined like most of our replacement taillights are. I recommend starting with your tow vehicle by using a Circuit Tester, like part # PTW2993, to make sure that the 5-Way on your vehicle side is fully functioning.

Moving on to your trailer, I would start by using the circuit tester to see which of those wires are not working on the harness that is pictured. Whichever wires are not getting a signal need to be traced back towards your 5-Way wiring harness on your trailer. Check for places where the wires might be corroded, exposed, bent, or damaged. If there are any spots that need to be replaced, you can do so with 14 Gauge Wire # DW07550-1 and Butt Connectors # DW05744-10.

Another option is that the harness that you are holding in the picture could be damaged and you might need to replace it.

I have attached some demonstration videos for you to view as well as some links to a helpful article and our taillight selection.

expert reply by: Jon G