How to Test to Determine Correct Wiring for 7-Way Vehicle Socket

Question:

Somebody please call and help me Ive been pulled over six times in the last three days I am a plumber I run a lot of service calls and I literally have been giving six tickets in the last three days at $160 apiece and help me wire this thing correctly. Right side T lights not wkn and blowing truck fuse 20 amp

asked by: Kyle D

Expert Reply:

There are three common ways a 7-way trailer connector can be wired; these depend on the type of application. For the most common, the RV standard, the function carried on each of the pins is shown in the photo I linked for you. This wiring scheme and the two others are all shown in the linked article on trailer wiring.

Since you have had a fuse blow it does sound like one or more of the circuits on your truck has been overloaded by the power draw from the trailer lights.

Keep in mind that wire colors are NOT always a reliable way to know what signal you will find on any given wire. There are common conventions for wire colors, such as a blue wire usually handling trailer brakes, but that does not apply in all circumstances. Use of a circuit tester like # PTW2993 will allow you to confirm which vehicle signal is carried on each wire to then allow you to connect each to the appropriate pin on your 7-way socket.

Have a helper activate each function, like the right turn signal for example, one at a time while you apply the tester. Once you know the function you can connect that wire to the correct pin on the 7-way. You can if you like test the trailer in a similar fashion, not with the tester but by simply applying 12V power from a battery or other source to each circuit on the trailer to see what light activates.

expert reply by: Adam R