Should the Blue Trailer Connector Wire be Hot All the Time

Updated 02/02/2018 | Published 02/01/2018

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Question:

Is the blue auxiliary wire to trailer hot all the time?

asked by: Lonnie

Expert Reply:

The only wires that could be hot all the time on a trailer connector is the 12-volt hot lead, which is usually a black wire, and, if applicable, the auxiliary power wire, which is normally yellow or purple. The blue wire is usually for electric trailer brakes and if it is hot all the time that would indicate a short.

I have included a link to our help article on trailer wiring that has numerous diagrams showing the functions of the pins for many trailer connector styles. You can't always go by color though, so it is recommended to test connectors using a circuit tester such as # PTW2993, or a meter if you have one, to verify functions.

expert reply by: Michael H