Troubleshooting Trailer Running Lights with 2002 Ford F-250

Updated 07/15/2015 | Published 07/14/2015

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Ford Replacement OEM Tow Package Wiring Harness, 7-Way (Super Duty)

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Hook Probe Circuit Tester

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Question:

In the 2002 f250 there is only a fuse panel under the steering column. I replaced fuse 38 but still no trailer running lights. There is very little about the 2002 solution.

asked by: Brian

Expert Reply:

First, we will want to determine where the problem is originating. The best place to start is at the vehicle. You will want to use a circuit tester, like # PTW2993, to test the trailer connector at the back of the vehicle, without the trailer hooked up. The tail and running lights should be connected to the top left blade in the factory 7-way, approximately at the 11 o'clock position. If there is no power to this wire while your running lights are on, then the problem is with the vehicle, not the trailer. If there is power at the connector, then the problem is somewhere on your trailer.

If the problem is on the vehicle, there are a number of spots along the wiring to check. You will want to check the harness that plugs into the connector to make sure the power is reaching that harness. If you have power there, but not at the connector, then the connector is bad. If there is no power at the harness, you will want to test the factory vehicle wiring.

You may have a relay somewhere that has gone bad. Use your owner's manual to determine which relay is for the trailer tow package running lights. Based on my research for your 2002 F-250, the trailer tow park lamp relay is in 205 of the passenger compartment fuse panel, the trailer tow backup lamp relay is in spot 204, the trailer tow left-hand turn/stop is in 210, the trailer tow right-hand turn/stop relay is 212, and the trailer tow batter charge relay is in 305. If you find all relays working correctly, then you would need to take the vehicle to a qualified mechanic to have it checked out.

If you determine you have running lights at the trailer connector on the truck, then the lights on the trailer are the problem. The first thing to check would be the ground to the trailer frame. If that doesn't solve your issue, inspect the trailer wiring for any damage.

If none of these work to solve your light problem, you can get back to me with the results of this troubleshooting and we can go from there.

expert reply by: Victoria B