Will a Brake Controller Stop a Trailer From Rolling Down a Hill into a Tree

Question

Question:

I installed a brake controller on my tow dolly. It is a dc modulator that controls a voltage 0 to 12 v to trailer blue and white lines. When moving the trailer forward even downhill, the brakes work as expected. When I pushed the trailer backward downhill, the brakes didnt work. My trailer ended up crashing onto a tree that stopped it. My question to you: The electric brakes do not work in reverse? I saw a video in which one of your experts explained electric brakes work in both directions. Please help me figure out about my brakes on 2021 MM 2108DS. Thanks! Liao

asked by: Liao C

0

Expert Reply:

Hey Liao, yes trailer brakes do work in reverse. I would assume what went wrong had to do with the brake controller more than anything. The brake controller would need power and ground which it was probably getting from your tow vehicle when connected via the trailer wiring but if your trailer was disconnected and able to roll by itself the controller wouldn't have any power to activate the brakes nor would it have anything to tell it to stop if that makes sense.

expert reply by: Jameson C

0

Liao C.

6/3/2025

Actually, I tested on the voltage while pulling the trailer forward and pushing it backward. I used an external battery to the controller. The trailer battery was not used. When pushing trailer backward on level ground, the brakes worked. It was when I pushed it backward down a slope, the brakes failed to stop it. I hope this gives you more details. Thanks for your time!

Jameson C.

6/3/2025

@LiaoC What was powering the brake controller when it was rolling down the hill?

Liao C.

6/3/2025

@JamesonC, It was a 30 AH LiFePO4 battery connected to the supply side of the controller (PWM). The device side of the PWM was connected to the blue and white lines of the trailer's 7 pin plug.

Jameson C.

6/3/2025

@LiaoC What was signaling the brake controller to apply the brakes? Is it a wireless brake controller that you had a wireless remote for that you were trying to press the override on?

See All (8) Replies to Liao C. ∨

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Will a Brake Controller Stop a Trailer From Rolling Down a Hill into a Tree

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