Brake Lights Not Working After Installing New Lights on Jet Ski Trailer  

Question:

Expert Reply:

Many times the cause for odd behavior from trailer lights is a bad ground connection. A weak ground can let some light functions work while others do not. I suggest that first you carefully check that the ground for each of your lights as well as the main trailer harness ground are all solidly connected to a clean bare metal surface on the trailer frame. If the trailer is aluminum, or has a tilt bed, then you may need to run a separate ground jumper wire between the two sides of the trailer. You can also run a ground wire from your lights right up to the trailer connector to see if the ground is the issue.

It is also wise to check the condition of both your vehicle and trailer connectors. Sometimes connectors can develop corrosion that can cause a short. Look for any discoloration on the vehicle socket and the trailer plug - even slight greenish or whitish discoloration - and clean as needed. Also check the wires on the trailer for any signs of worn or cracked insulation, especially in places where the wires touch the frame. Repair or replace any damaged wires.

You can also test the trailer socket on the vehicle using a tester like # PTW2993. Please refer to the linked video for illustration of how to do this. Disconnect the trailer and have a helper activate the brake lights while you apply the tester. You can refer to the linked article on wiring to see the specific pins to test - depending on the type of connector you have. If you have a 7-way like what is shown in the linked picture you will want to test for a brake signal on the pins at the 3- and 9-o-clock positions. If you detect the correct signals when the brake is pressed then you know you need to focus on the trailer connectors, wiring and ground connections.

expert reply by: Adam R

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