Troubleshooting Trailer Brake and Turn Signal Not Working

Updated 04/08/2025 | Published 04/06/2025

Products Featured in This Question

Peterson LED Combination Tail Light - Submersible - 7 Function - 6 Diodes - Square - Passenger Side

(18)

$24.30

Replacement Rear Lens for Peterson 844 Series LED Tail Light - Red

(4)

$6.02

Peterson LED Combination Tail Light - Submersible - 8 Function - 7 Diodes - Square - Driver Side

(18)

$23.97

Question:

I hooked up my utility trailer to the truck. I wanted to check the trailer lights for braking, turn signals and running lights. I noticed the right side trailer taillight did not blink for a right turn signal! Also, no brake light function. The taillight is on if no action for braking and turning. I suspect a bulb issue but cannot figure out how to get to the bulb! It has two mounting screws in the back, that’s it Does the cover just pop off?

asked by: Edward L

Peterson Light
(click to enlarge)

Expert Reply:

Hey Edward! That looks like the Peterson LED Combination Tail Light # M844 and # M844L on your trailer. The lens is held on by four tabs which can be seen in the attached photo of the replacement lens # 844-252. It would also be worth double checking your ground connections since a loose ground is often the issue with symptoms like these. I would check trailer connectors as well to make sure no corrosion is present. If all of that checks out it could be a short in the wiring or even loose wiring at the back of the trailer light.

expert reply by: Robin H

Peterson Lens
(click to enlarge)

Edwardl

4/8/2025

Robin Thanks. I'll check on some grounding or loose wire issues. I guess the bulb, or bulbs not replaceable? Edward

Robin H.

4/8/2025

@Edwardl if it is the LED then no. It might be incandescent, not sure how old your lights are. Most designs had incandescent bulbs before switching to LED. If it has a bulb it should be pretty easy to identify and replace it.