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What Are Wire Functions on Factory 7-Way Trailer Connector on 2002 Ford F350


PLEASE HELP ! I am trying to find out what pins 6 and 7 are coming from on a 2002F-350 factory trailer harness connection on connector # 13A576 there is 2 blue wires and I know 1 is for trailer brake but cant find anywhere what the other one is from. Im thinking from brake controller but dont know how to wire it up, should I tie the 2 together? The schematics I have found both give 43 DB I assume dark blue but cant find anybody to tell me what they are. Thank you


Expert Reply:

The one and only truly reliable method to confirm what signal/function is carried on a vehicle wire is to test it. Wire colors are sometimes common to a certain lighting function; running light signals are often carried on a brown wire, for example. But wire color is neither consistent nor reliable as a means to determine the function carried. A circuit tester like # 40376 is the way to go.

If you refer to the linked photo showing a 7-way RV-style vehicle socket you will see the common function assignments for each pin location and wire color. I have also linked a video showing how to use a tester like # 40376.

Have a helper activate the vehicle light functions one at a time while you test. Ground the tester and apply the probe to each pin on the 7-way until you find the active circuit. You will then know what function is wired to what pin. It is not advisable to join any wires until you are certain of their functions.

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