Troubleshooting Trailer Lights
January 2013, TruckingInfo.com - Feature
One of the most common reasons for an officer to pull a driver over is for a faulty light. Below are some basic guidelines on how to troubleshoot some of the problems that may arise with a trailer lighting system.
Total lighting failure: No part of the system appears to be powered. Possible causes:
Burnt 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.1. 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. 2. Check for a good ground. 3. 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:
Burnt 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.1. 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.2. With the power on, check the pigtail for continuity.
- If the pigtail does not function, check the jumper that connects the pigtail to the harness.
- If the jumper does not function, check the main harness.
- Keep working upstream in the system until you get a connection that functions. From there you know the problem is downstream in the system. Lamps working intermittently and/or flickering: a single lamp or entire circuit Possible causes:
Small amount of corrosion build up; ground problem; short in wiring harness; loose pins in 7-way; loose wire in 7-way; problem in the tractor. 1. Visually check connections and wire jacketing.
2. Start testing from the front of the trailer beginning with the 7-way socket. Disconnect one piece of the harness at a time and check the circuit. Lit lamps that should be off: This is the most difficult failure to find. Possible Causes:
Electrical short, crossed wires or a bad switch. 1. Visually inspect all connections and wire jacketing.
2. Check the harness one piece at a time starting from the rear and working your way back up to the 7-way socket.From the December 2012 issue of the Phillips' Qwik Tech Tips newsletter. To subscribe to Phillips' Qwik Tech Tips newsletter, visit www.phillipsqwiktechtips.com.