Tail Lights and Side Marker Lights Malfunctioning on Boat Trailer

Question:

boat trailer lites left and right turn signals work both brake lites work,no tail lites or side marker lites work,replaced bulbs and checked ground itis ok.Can you help me out ?

asked by: Tony

Expert Reply:

The first thing to do would be to determine if the wiring issue exists on the trailer, or with the tow vehicle. Use a circuit tester, like part # PTW2993 and test the socket on your trailer connector that carries the signal for the running light circuit. If you have a 4 or 5-way flat, test the socket that corresponds with the brown wire. If you get voltage at this location while the vehicle headlights are on, the wiring problem is on the trailer. Check the connector on the trailer, and ensure it is not corroded or damaged. The brown wire typically carries the signal for the running/marker lights, use a circuit tester on this wire just rearward of the trailer connector, to make sure that the signal is passing through the trailer/vehicle connection. Examine this wire as you get back to the lamps, looking for pinched or loose wires or missing wire insulation.

If you are not getting power at the trailer connector on the vehicle, the problem will depend on the vehicle and how the trailer connector is wired. If the suggestions I have provided above do not turn up anything, please respond with the year, make and model of your vehicle and we will explore some other options. It would also be helpful to know which trailer connector you currently have on the vehicle and whether it was factory installed or aftermarket.

expert reply by: Mike L