Wiring Side Marker Lights on Trailer as Turn Signals

Question:

Is there a way to have a side marker light also flash when that side directional is on without turning on with the brake? Also when adding reverse lights to an RV should I use the reverse wire on the 7 way to directly power the lights or run it through a relay? I am using aftermarket fog lights. 55 W H3 halogen

asked by: Bob

Expert Reply:

Using a relay would be the way to go if you wish to use those fog lamps as reverse lights. You would want one input on the relay tapped into the reverse light circuit, and one leg ran to a 12-volt power source.
There would be no really simple method of getting a side marker light to serve as a directional signal without having it light when the brakes are applied.
How to make your connections will depend on the taillight system of your tow vehicle. If your vehicle has amber colored turn signals, you could simply tap into each turn signal light behind the tail light assemblies and run a lead from each side to terminate into a 2 pin connector. You could zip tie this connector to your other trailer connector. On the trailer side, use the other side of the 2 pin connector to run to each side marker.
If your vehicle has a 2 wire system which uses the same bulb for the brake and directional signal, you would need a vehicle to vehicle converter, part # 118158 installed on the trailer. The yellow wire on the input side would tap into the left turn signal circuit, the green wire would tap into the right turn signal circuit. On the output side, you would then run the yellow wire to the marker light on the left side of the trailer, and the green wire to the marker light on the right. The red wire would not be used, just tape the end off and bundle that wire up out of the way.

expert reply by: Mike L