Wiring Vehicle and Trailer Connectors

Question:

Can you explain how to wire a 7 pin trailer plug and trailer brake on a 1975 f250 that’s all original thanks

asked by: Henry T

Expert Reply:

Wiring 7-way connector # PK12706 on your trailer and 7-way socket # PK12-707E on a vehicle like your 1975 Ford F-250 is simple; all you will need is an auxiliary 12 volt battery and a circuit tester such as # PTW2993.

You will need to wire the connectors via function, which are displayed in the accompanying photo. To determine the functions of the wires run on your truck, have a helper engage them while you use the circuit tester and attach them to the 7-way Trailer Socket # PK12-707E.

The same thing will need to be done on your trailer but this is where the 12 volt battery comes in. Just run a jumper wire from the positive post of the battery to the wires on the trailer to determine what their function is and attach them to the Trailer End Connector # PK12706.

Trailer brakes will have two wires coming out of them, one for ground and the other is power (it should not matter which wire you use) and you will connect the power wire from the brakes to the electric brake output on connector # PK12706.

I have added a link to a help article on trailer wiring which I highly recommend checking out as well as it has additional diagrams which may be useful.