Troubleshooting Trailer Lights After Installing Hopkins Adapter 4 Pole to 7 Pole and 4 Pole # 37185

Updated 09/12/2014 | Published 09/11/2014

Products Featured in This Question

Adapter 4-Pole to 7-Pole and 4-Pole

(659)

$61.55

LCD Digital Circuit Tester

(26)

$26.67

Question:

Trailer turn signals, running lights, and brake lights are not working after installing 37185. I have 12 volts running to the black wire for the electric brakes but the running lights and turn signals should be coming off the flat 4. The lights on the trailer arent working. Its a 2001 Coleman Mesa popup camper. Unless the camper will not let the lights turn on when its open Im just testing everything at this point.

asked by: Nick J

Expert Reply:

You will want to test the Escape's 4-pole wiring, that connects to the Hopkins Adapter # 37185, to determine if the vehicle is properly sending the lighting signals to the adapter. Use a circuit tester like # PTW2992 on each of the wires on the vehicle's 4-pole harness. Ground your tester to the exposed pin for the white ground wire. The yellow wire should carry left turn and stop light signals; the green wire should carry right turn and stop light signals; the brown wire should carry a running light signal when the Escape's headlights are on.

If the correct signals are present on the vehicle's 4-pole, connect it to the Hopkins adapter and test the pins on the 4-pole portion of the adapter. If these lighting signals are not present on the 4-pole portion of the Hopkins adapter, then it may be damaged. If the vehicle is not sending out the correct signals then your 4-pole vehicle harness may be damaged. Please advise your Escape's model year if you wish me to recommend a new harness.

Trailer brake, 12V power and a reverse light signal are carried on the 7-pole only (not on the 4-pole). These functions require additional connections to the adapter's wire leads: blue is for trailer brakes and connects to the brake controller's blue output wire; black is for 12V trailer power and connects to the vehicle battery through a fuse or circuit breaker; the purple wire is typically used for reverse light circuits for a trailer's backup lights or to operate a reverse lockout solenoid on a surge coupler.

You can also directly test the trailer by applying power one at a time to each circuit on its connector.
If you wish you can use the vehicle's battery or a spare. If the lights and brakes on the trailer work properly when directly powered in this manner then you know there is a problem in the adapter.

I have linked you to a help article on wiring and also to a video showing how to use a tester.

expert reply by: Adam R