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Trailer wiring issues


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The male trailer plug has slots cut in the 7 pins which can be opened a little with something thin to give better contact in the female plug.

I usually just push a store/credit card into the slotsimage.jpg as it opens them up perfectly I found.

With both the female/male plugs make sure the pins,wires,screws are clean and tight to give the best electrical connection possible.


My issue was the end cap had separated from the glass causing an intermittent fault with the brake lights. image.jpg


1: No power at one or all car trailer plug terminals when testing.

-Check ground for cars trailer plug has good clean contact and wiring is intact.

-Open car plug and check all wires terminals are clean and tight with no breakages.

-Trace wire/s back to vehicles wiring harness splice/plug and check again for power.

-Check all soldered joins,connectors are secure.

-If there's power at the vehicle harness but not at the plug the wiring from the plug has most likely got an internal break or has a short.

2:No power at one or all trailer plug when testing.

-Check car plug terminals for power.

-Open trailer plug and check wires,terminals and screws are clean and tight.

-If there's power at the car terminals you have broken/loose Terminal/s.

3:No power at trailer light bulb holders.

-Check for power at trailer plug.

-Examine lights for loose/corroded rivets/terminals.

-Wiring may be corroded/damaged in between the tail lights and plug.(In this case I'd check for continuity from the trailer light wiring to the trailer plug with a multimeter).

-Lights may have corroded internals.

There's a heap of other things that can be tested like checking for voltage drops which usually indicate corroded or broken strands of wire but these basics will give you somewhere to start.

If the trailer wiring is corroded to far it's often easier to just replace it.

Hope this helps some one out as trailer lighting issues are quite common.



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