Troubleshooting Trailer Tail Lights Not Working When Brake/Turn Lights Work

Updated 03/05/2019 | Published 03/03/2019

Products Featured in This Question

Hook Probe Circuit Tester

(66)

$12.94

16 Gauge Primary Wire - Black - Per Foot

(63)

$1.06

Deka Heat Shrink Butt Connector - 16-14 Gauge - Nylon Insulation - Blue - Qty 5

(1141)

$9.09

Question:

HAVE SIGNAL BRAKE FLASHERS BUT NO TAIL LIGHTS HAVE NO POWER AT THE PLUG CANT FIND A BLOWN FUSE HELP

asked by: KIRBY G

Expert Reply:

Since you have brake and turn but not taillights, the issue can be a fuse, a relay, bad wiring, or a weak connection. I recommend you first start with the wiring connection by cleaning it up with some sandpaper or steel wool, and then testing the pin for power.

If you don't have power, I recommend first checking your ground connection at the trailer plug. A weak ground connection can cause some functions to work and others not to work. Next, I recommend checking your owner's manual for a fuse or relay location that has to do with trailer taillights/running lights. If there is nothing in the fuse or relay information for trailers, then I recommend tracing your wiring from that pin location back using a circuit tester like # PTW2993 probing the wire every few feet. When you find the short, replace the wire with # 16-1-1 sold by the foot and butt connectors # DW05744-5.

If you tract to a converter box or module and you test signals coming in but not coming out, then the module will need replaced.

expert reply by: Jason S