Trailer and heavy truck lights and electrical repair

Common situations

• Trailer tail, brake or turn lights out
• Damaged or corroded 7-way plug or socket
• Trailer pigtail torn off or cut
• Marker or clearance lights out
• A fuse that keeps blowing
• Corroded ground connection

What the technician does

The technician traces the fault with a multimeter, replaces the plug, socket, pigtail, lights and common fuses, and redoes corroded connections.

A full light check is done with you before you leave.

A quick check before you call

Look at the tractor’s fuses and inside the 7-way plug: green, corroded or bent pins often explain a trailer with no lights. Note which lights are out; it helps the technician bring the right parts.

What needs a shop

A wiring harness damaged over a long length or a failed electronic module needs shop diagnosis. The technician will tell you on site.

To speed things up

• Which lights are out, and on which side
• Whether it is one trailer or every trailer the tractor pulls
• The condition of the plug and cable between tractor and trailer
• Whether a fuse was replaced recently