Troubleshooting trailer lights

Service & Repair Truck Parts & Service Staff February 3, 2013

DOT regulations state that any and all lights on a tractor must be in working order, including lights on a connected trailer.

To make sure those lights are operating at peak efficiency at all times, you must check them periodically and perform regular maintenance.

Below are tips from Phillips Industries on how to get lights working when they malfunction.

Total Lighting Failure: No part of the system appears to be powered.

Possible Causes: Burned out light bulb causing a break in the system; ­corrosion in harness, light plug or pigtail; ground problem; hydraulic lock from too much dielectric grease; bad spot in wiring harness; issues in the 7-way plug; issues from the tractor.

Check to see if you have power at the 7-way of the trailer. If there is no power there, check the back of the 7-way cable from the tractor. If there is no power there, check the 7-way socket on the tractor.

Check for a good ground.

Check the condition of the 7-way ­connector.

Check for a secure connection.

Check to see if corrosion is present.

Single Lamp Failure: Problem appears to be isolated to one lamp.

Possible Causes: Burned out light bulb; corrosion in harness, light plug or pigtail; ground problem; hydraulic lock from too much dielectric grease; bad spot in wiring harness; issues in the 7-way plug; issues from the tractor.

Check the lamp with a lamp tester. If the lamp functions, try re-installing it. If the lamp is not functional, move on to step two.

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