Wiring a 7-Way Connector for a Dome Light In a Enclosed Trailer with a 4-Way Connector

Updated 02/22/2010 | Published 02/21/2010

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Question:

Im trying to add a dome light to my enclosed cargo trailer. The trailer had a 4 pin connector and I changed it to a 7 way connector and added an extra wire specifically for the dome light. I got all the lights on the trailer to work properly but cannot get power to the dome light. I connected the extra wire to the + pole on the 7 pin following the diagram on the truck and the light does not work. The extra poles are for back up lights and trailer breaks. What am I doing wrong?

asked by: toothpeckman

Expert Reply:

If your truck has a 7-Way connector from the factory the #4 connection in the 1 O-clock position will be the 12 volt power connection. We have diagrams of the vehicle side and trailer side 7-Way connectors on our wiring page that will show you where to connect the 12 volt battery lead. You will need to run a 10 gauge wire, item # 10-1-1, from the positive post on the vehicle battery through a 40 amp circuit breaker, item # PK54540, to the proper connection point, #4, in the vehicle side trailer connector if your vehicle does not have power ran from the factory. You will then need to run a wire, at least 12 gauge, item # 12-1-1, to the dome light in the trailer from the proper connection in the trailer connector.

The center pole in the trailer is usually used for reverse lights or reverse lockout on trailers with surge brakes and the #2 connection is usually the blue brake feed connection for trailer brakes.

expert reply by: Robert G