Troubleshooting Dim Trailer Left Turn Signal

Updated 02/01/2022 | Published 01/28/2022

Products Featured in This Question

Optronics LED Trailer Light - Brake, Tail, Turn - Submersible - Oval - Red

(1692)

$12.44

Loctite Bulb, Lamp, and Electrical Connection Dielectric Grease - 0.33-Oz Tube

(133)

$9.22

Question:

When I use my left turn signal it’s dim but bright with the breaks and running lights. When I jump it with a jumper from power to left turn pin it lights up. If I use an isolated box with a 7way tester it works but when I hook up to truck it’s dim. Ruth turn and break works fine only the left. Could I have a grounding issue with the trucks 7way?

asked by: Kenneth H

Expert Reply:

Yes, this could possible be an issue. Sometimes a faulty ground can limit the amount of current that can flow to the lights. It can also cause your lights to behave in unpredictable ways.

My recommendation would be to hook up a 12V, well charged, battery directly to your trailer connector. Apply the negative terminal to the connector ground and then apply the positive terminal to the different light pins. If the lights are still dim, your problem is in the trailer wiring. If this is the case, you should check your trailer's ground wire first. It should be clean and attached to a bare metal surface. If you have corrosion, you can sand off that spot. You also might want to sand off any paint, so you can attach the ground wire to the bare metal at that point. You can use solvent to remove any grease or contaminants from the wire. The last thing you should do is to apply dielectric grease, part # LT37534, to your connection.

If you have a multimeter, you can check the voltage on your trailer connector. If you read less than 12V, you can check the ground on your vehicle as well.

I have included a product description link, a video demo link, and a weblink about trailer wiring below.

expert reply by: Mark Smith