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Process for Testing Caravan Wiring for Determining Function on Each Wire

Question:

Is there a process to follow when the colour coding for the wiring on the van doesn’t match instructions on how to hook it up, to the 7 pin flat. For example, there is no brown wire, the green wire wasn’t even in use. What steps can I take to try and fix the issue? The van is an 85 Windsor pop top. Cheers.

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Helpful Expert Reply:

Yes, you can use a process of testing your wiring with a circuit tester to confirm what electrical function each one carries. Wire insulation color is not a reliable way to know what that wire does so a probe tester like # PTW2992 is the best way to eliminate guesswork. You can refer to the linked video to see how the tester is used.

When testing a vehicle it is easiest to have a helper activate a function while you test the wires to find the wire that carries that function. For instance, if the van headlights are turning on this should activate the trailer running light circuit. Most often this is carried on a brown wire, but again, wire colors could be different.

If it is the trailer's wiring you're looking to test, the you can use a vehicle battery or a well-charged spare 12V battery to apply power to the trailer's wires to determine their functions. Find the main ground wire on the trailer (the one that connects to the frame) and connect it to the test battery's ground terminal. Then one by one apply the positive battery terminal to the other wires to see which function activates. You'll want to use some tape to label each wire as you go through the testing process.

The battery testing process on the trailer can be made easier with a set of battery jumper cables like # PTW1675 and a couple of lengths of wire like # 10-1-1.

I linked a photo and helpful article on trailer wiring to show you how the 7-way trailer connector format is usually configured.

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