Troubleshooting Trailer Wiring on 2014 Dodge Ram 1500

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Hook Probe Circuit Tester

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Question:

Hello i have a 2014 dodge ram 1500 i have used this trailer extensively and i had lights last time i used it and now nothing i checked the plug and had no power to any of the tabs i checked the fuse and it was fine but had no power going to it on the cover it does not show trailer relays but getting a diagram from the parts store it show it has a relay for right light one for the left light and one for the trailer brake and one more for something else do you think all the relays went out at once/ and these relays are not serviceable. i think they are integrated into the fuse box on the bottom any ideas?

asked by: John

Expert Reply:

It would be unusual for all three relays in your 2014 Dodge Ram 1500 (or any other vehicle) to all go bad at once. If this did happen I would suspect the vehicle or trailer wiring/connectors. It is possible for internal corrosion to build up that could cause a short-circuit. This can occur on the visible parts of the sockets or plugs but it can also develop on the inside of these connectors, where it is very hard to spot. With enough exposure to the elements the trailer socket or plug could develop such an issue and to look at these connectors you might never know it.

You may also want to check the wiring/plugs that lead to the socket on the truck. Unplug it and check for damage, corrosion or trapped water - anything that could interfere with signal transmission. You might also trace the wiring on the truck, from the trailer connector as far forward as you can, looking for signs of damage from road debris.

If you have a circuit tester like # PTW2993 you can test the truck wiring at the connector contacts and then continue testing as you move forward; to the wiring that feeds the trailer socket, etc. Doing this will tell you at what point in the overall wiring setup the signals are being lost.

You can also test the trailer by itself when it is not connected to the truck. Use the truck's battery or a well-charged spare if you have one to apply 12V power directly to the trailer's plug. Apply power to one circuit at a time to see if they function. If not then the issue could be on your trailer, say a bad short that took out your relays/fuses. In this case repair/replace any damaged wiring on the trailer.

If you need a new 7-way plug it is easy to install one using the # HS381-9000 which has a 7-way plug and a junction box for handy splicing.

expert reply by: Adam R