Troubleshooting Trailer Connectors That Do Not Pass Running Lights or Turn Signals  

Question:

Expert Reply:

The best way to troubleshoot trailer wiring is to first test your Acadia's 4-pole WITHOUT the Curt adapter. This will let you know if the signals are reaching the adapter. Even though the LED test lights may come on, since these take so little power to light up it could be that there is a small residual voltage in the system that is causing them to illuminate even when no actual running light or turn signal is reaching the adapter.

You can use a tester like the # PTW2993 to check the Acadia's 4-pole. Please refer to the linked photo and video for illustration of the connector and testing method.

If you find that the vehicle 4-pole has all of the correct signals, then check that your adapter connection is tight and free of corrosion, dirt or moisture. If your contacts are all clean you can use dielectric grease like # LT37534 to protect them. Then test the 7-way contacts on the adapter in the same way that you did on the 4-pole. If you have signals going in but not coming out then the adapter is bad.

If your Acadia's 4-pole does not pass the correct signals you'll need to check all the connections for that harness and you may need to clean the contact surfaces of any greenish or whitish discoloration; even this slight corrosion can interfere with signal transmission. If this does not help then you may need to replace the factory 4-pole with # C55515.

You can also easily test the trailer lights directly by applying 12V input power from the vehicle or another 12V battery directly to the trailer plug. Apply +12V power to one circuit at a time while the negative wire is connected to the ground pin. If your vehicle 4-pole works and the trailer lights work when tested in this way then you know the adapter need to be replaced.

expert reply by: Adam R

0

click to enlarge