How to Identify Wiring Circuits on 1995 Harco Trailer  

Question:

Expert Reply:

Typically trailer wiring uses a white wire for ground but there is never any guarantee that a given trailer's wiring uses the common color assignments for its functions. You can check to see which wire is connected to the trailer frame. Usually a brown wire handles the running lights, yellow and green the left- and right-hand stop/turn lights. For reference the linked article shows you the usual wiring/pin configurations for 4-pole, 5-pole as well as other wiring formats. 4-Pole setups do not include a brake circuit but a 5-pole (or 6-way or 7-way) can.

The best way to know for sure what any wire/circuit on the trailer does is t apply 12V power to it and note which light/function is activated. You can use your vehicle's battery or a spare. Apply the ground wire to the negative terminal and apply the other wires, one at a time, to the positive post and see which lights comes on. If the red wire is for electric brakes and if they are functional you should hear a gentle humming from their magnets when power is applied.

It is often easier to re-wire a trailer rather than try to figure out what has been done with its wiring, especially on an older trailer that may have had multiple owners. If you want to go this route you will find it easiest to install a junction box like 7-way type # HS381-9000 or standard junction box # 38656. You'll also want ring terminals like # 44-5310A and # DW05737-1 for the various wire gauges on the trailer.

expert reply by: Adam R

0