Preferred Method of Grounding Trailer Lighting Circuits

Published 11/04/2015

Products Featured in This Question

Optronics Combination Trailer Tail Light - 6 Function - Incandescent - Red Lens - Passenger Side

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$7.88

16 Gauge Primary Wire - White - Per Foot

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Ring Terminal -16-14 Gauge - 1/4" Ring ID - Qty. 1

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Combination Trailer Tail Light - 7 Function - Incandescent - Square - Red Lens - Driver Side

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Question:

Hello. On ST8RB and ST9RB and others that ground itself via bolts, would it be better to attach white ground wire on the mounting stud in lights and run it forward to tong if trailer, in this case, wire junction box, would it be better and to make sure its grounded as a safeguard? Would the extra ground wire wouldnt hurt, other than making sure its grounded? and prevent me from constantly replacing fuses on truck side, which narrowed down to lack of positive ground in trailer side

asked by: Robert

Expert Reply:

Running a direct ground up to the trailer tongue or junction box would certainly work, but the only time I'd see that as being necessary is if the lamps were connected to a non metallic structure or a metallic structure that wasn't directly connected to the trailer frame. If the lamps aren't connected to a metal structure in direct contact with the trailer frame, you can use a short length of # DW02359-1 wire with a # DW05702-1 ring terminal on each end to serve as a jumper wire that joins the mounting stud of the lamp to the trailer frame.

When the lamps are installed on metal that's in contact with the trailer frame, the circuit is using the metal trailer frame itself as a ground circuit, so running a separate ground circuit isn't really necessary. If the trailer in question has a tilting tongue or a tilt bed, sometimes the pivot point between the moving and stationary portion of the trailer becomes worn, leading to a poor ground connection. In that case, using a jumper to join the moving to the stationary part of the trailer will fix the issue.

expert reply by: Mike L