RV Education

RV Resources and Tech Advice

Mike Wilson is a RVDA Certified Master RV Tech. with over 25 years experience and now he's sharing his knowledge with you.
Mike is the president of Wilson RV and developer for The RV Help Desk.

Towing Series
Tow Dolly Towing 4 Wheels Down

Tow Lights and Wiring Tail Light Wiring

Braking Units M&G Braking Unit Air-Brakes

Braking Units

“Brake Box”
There are several brake boxes available for your towed vehicle.
Blue Ox, Roadmaster and Brake Buddy are 3 examples.
A brake box is a simple to use device that sits on the front driver’s floor of the vehicle.
They are powered from a 12 volt outlet or can be hard wired if an outlet is inconvenient or doesn’t exist.
These boxes operate from an inertia mechanism within the box. There are some differences between manufacturers.
Analog electronics were used early on, but now digital has become popular.
Digital control allows the braking unit to react quicker and apply the brake more “in sync” with the RV.
The unit operates similar to trailer surge brakes. This means it senses movement.
When your RV momentum slows, the inertia switching device within the unit senses a decrease in speed and activates the braking unit
which applies the brake pedal in the towed vehicle. The braking units use air pressure supplied from an internal air pump to apply the brakes.
The air pump operates from a 12 volt DC power source, hence the need for a 12 volt connection.
The amount of brake effort depends on the momentum change. This is where it gets complicated.
Manufacturers have been trying to make the braking units operate similar to the RV’s brakes.
Since there is no actual connection to the RV’s brakes, it is difficult to do.

Technology has helped to make these units operate closer to the RV’s braking. The latest units now use electronic controls inside the RV to allow driver input.

*Breakaway

A breakaway is a safety device connected to the towed vehicles braking system.
It also attaches to the RV at the rear by cable. If the towed vehicle would disconnect from the RV while towing,
the breakaway pin will be pulled by the cable activating the braking system.
Breakaways are required by law in some states and Canada. Breakaways may be optional with most systems.
This is an item that will be mounted and hard wired to the towed vehicle. It needs to be center mounted at the front.
I always try to mount it on the base plate when possible. It should be screwed on and double nutted to allow it to rotate from side to side.
This will help align it to the RV no matter which way it could move if detached. There are 2 wires that will run from the breakaway to the braking unit.
Be sure to have a professional install the breakaway if you’re not sure how to do it correctly.
Typical installation takes 1-2 hours. It is the most difficult part of the brake box installation.

Advantages of braking boxes

Versatile: Can be transferred easily between vehicles

Ease of installation: Can be self installed. * breakaway may be required

Disadvantages of braking boxes

Battery run down in towed vehicle: In my opinion, manufacturers of braking units in general tend to exaggerate battery run down.
My experience has been that braking units tend to cause battery run down much quicker than manufacturers disclose.
We typically see battery run down occurs daily from braking units powered from the towed vehicle.

Brake control: Brake boxes don’t have direct control from the RV.
Relying on inertia can make the braking unit activate when not wanted. (I have also seen the braking units “hang” on and not release)

Breakaway switches tend to rust and corrode in winter driving conditions