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Troubleshooting No Stop or Turn Signals on an Enclosed Trailer With a New 7-Way Connector  

Question:

I have a enclosed trailer with the new plug 7 pole connection.I have tunning lights but cannot get the turn signals and brake lights to work again.they were working just a few day ago.but they just stop working....any help appreciated..

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Expert Reply:

The main culprit for trailer light failure after a new installation is a poor ground connection. Since you recently had a new 7-pin connector installed on your trailer, I would make sure that the ground wire is attached to a clean, bare metal surface on the trailer frame. I would also make sure the lights are grounded properly.

If the ground connections look fine, you will want to test the tail light circuits themselves using a circuit tester like part # PTW2979. First, test the 7-pin connector on your tow vehicle. This will ensure that the issue is on the trailer and that the connector on your tow vehicle is working properly. I have attached a photo of the pin functions on a 7-way trailer connector for you to reference.

If the 7-way connector on your tow vehicle is not working, then we know the issue is on the vehicle wiring. If you have a factory tow package, there could be a blown fuse. If you have aftermarket trailer wiring, you will want to test the wires going from the connector to the appropriate circuit looking for any loose connections or damaged wires.

If the connector on your tow vehicle works properly, then we know the issue is on the trailer. To begin troubleshooting the trailer, hook the trailer to the tow vehicle. Have a helper activate each tail light function as you test the wires on the trailer. Since you had a new connector installed, test the wires directly behind the connector to see if power is able to pass through the connection between the trailer and tow vehicle. Probe each wire using the circuit tester. If you do not have power for the turn signals or brake lights coming through the trailer connector, then the issue is likely with the new 7-way connector.

If you do have power past the connector, work your way toward the tail lights on the trailer and probe the wires at random points. Also keep an eye out for any pinched, frayed or damaged sections of wires that could cause a short. This will show you where the power terminates before reaching the tail lights.

I would disregard the colors on the diagram that I attached because trailer manufacturers do not always follow an industry standard when it comes to wire colors so it is important to test for function rather than matching up color. I have attached a trailer wiring diagram as well as our FAQ article on trailer wiring for you to review. These should help you when you are troubleshooting your trailer wiring.

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John H
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