Troubleshooting Trailer Brake Lights and Turn Signals Not Working After Installing 7 Way on Vehicle

Updated 07/09/2020 | Published 07/07/2020

Products Featured in This Question

Cordless Circuit Tester

(15)

$19.43

10 Gauge Wire - Blue Primary - Per Foot

(108)

$1.65

Deka Heat Shrink Butt Connector - 12-10 Gauge - Nylon Insulation - Yellow - Qty 10

(1146)

$13.21

Universal Installation Kit for Trailer Brake Controller - 7-Way RV and 4-Way Flat - 10 Gauge Wires

(3470)

$118.67

Question:

I recently made a purchase for a 7 was plug/harness for my GMC Acadia as well as the hitch and everything to go with it it all mounted up nicely plugged the harness in and hook up my camper and the running lights all work but not my brake or turn signals???

asked by: Gary L

Expert Reply:

If you've just installed a 7 way connector like the # ETBC7, you'll want to start by testing the plug on the vehicle using a circuit tester like the # PTW2979 to make sure that each pin is operating properly; you can refer to the photo attached or a helpful article that I've linked for information on testing the circuits. I would also recommend making sure that your ground wire on this harness is firmly grounded to a paint and rust free spot, as ground wires are the most common cause for faults like this since. The harness can supply power to the running lights since they require a small amount of amps, but adding the other lights into the mix creates complications that can pop up when the harness isn't properly grounded.

If all of the circuits on the harness are properly functioning when you test them, this issue is going to be on the trailer, so you'll want to trace the wires on that circuit back to make sure they are not damaged in any way; you'll want to replace any cut or damaged wiring as needed with something like the # 10-1-1 (sold by the foot) and heat shrink butt connectors # DW05745-10.

If you can confirm that the wiring on the trailer is in good shape and all of the circuits on the 7 way connector are working, but the lights still are not, please let me know and I can give you a few other things to look at.

expert reply by: Erik B