What causes trailer running lights to not work?

Expert Reply: It could be a tow package fuse on the vehicle. Use the owners manual to find the locations of fuses/relays related to the tow package wiring to check them and replace as needed. If the issue is not a fuse or relay then you can test the vehicle side trailer connector using a circuit tester such as # 40376.

How do you check trailer lights without trailer?

You can use your multimeter or just a simple test light. Depends on how you wired it. Each circuit will still show voltage without the trailer attached ie turn on a blinker and that junction in the plug will show voltage on your meter.

Why do all trailer lights work except running lights?

Question: You will want to make sure the ground has contact with a bare, clean, metal surface of the trailer frame. If there is any rust or corrosion at the light ground, try relocating the light grounds to a suitable location.

What color is running lights on trailer?

Trailer Wiring Has 5-Wires White, Yellow, Green, Yellow/Brown, and Green/Brown On a 4-Way flat trailer wiring harness, white is the ground, brown is running lights, yellow is left turn signal and green is right turn signal.

Does trailer need to be on hitch for lights to work?

My question is does the trailer need to be grounded to my truck for lights to work? In some cases trailer lighting will ground through the hitch ball but that’s typically only if the actual ground circuit is insufficient. This is not an ideal setup. It needs to ground through the wiring of the trailer harness.

Why is only one of my running lights working?

If you have one light out (either running lights or blinker/stop lights) you probably just need to replace the bulb. Remove the lens, replace the bulb and check it. If it works, you’re on your way.

Can you check trailer lights with a battery charger?

You would need to have a 12V power source and your jumper wire which will let you know if you have working trailer lights. The most common gauge trailer light wire for 4-way or 5-way trailer connector is 14-16. You will need to make sure that you secure the ground wire to the trailer frame.