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RV Help Desk


RV Education

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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

Air Brake Units For RV’s W/Full Air Brakes 

There are several braking units that will work with coach air brakes.
This article explains Blue Ox’s BrakeSafe and Roadmaster BrakeMaster units.
These systems are quite simple and work very well, with the braking unit operating in tandem with the coach brakes.
The two are very similar.

An air cylinder is used inside the towed vehicle to push the brake pedal.
The cylinder mounts to the floor or seat by a bracket and quick connecting pin.
In my opinion Roadmaster has an advantage here since they now have brackets available to bolt directly
on the driver’s seat for some vehicles. (With a seat bracket, it is not necessary to drill holes in the floor).
A rod attaches to the brake pedal using a spring loaded clasp.
An air line is routed from the front of the towed vehicle along the under hood area, then inside the vehicle
going through the firewall. A connector and bracket are provided to mount at the front of the towed vehicle
close to the tail light wiring connector. The line attaches to the air cylinder by an air coupling.
It should be routed along the sill plate to an area under the seat where it can be stored out of site when not in use.

On the coach end, the air supply will be teed into the air brakes. Be certain the coach can handle this system.
I recommend checking with the manufacturer of the coach to be sure they will allow tapping into the air brake system.
If allowed, hook into the air brakes near the rear of the coach close to one of the actuators at the relay.
The actuators are the air bellows that activate the braking mechanism.
I find in most applications there is a relay close by that has a plug in it.
Be sure the wear some type of hearing protection for the next step.
Simply remove the plug then have a helper activate the brake by pressing the brake pedal.
Be sure the air flow comes out of the fitting where the plug was removed only when the brake pedal is activated.
Use one of the adapters provided to connect an air line to the correct fitting.
In some cases you may need to find the correct style or size fitting from a parts supplier.
Route the air line away from any moving parts to the rear of the RV where a bracket and coupler can be mounted.
A coiled air hose is provided to make the connections between vehicles.

There is an optional indicator light provided to mount inside the RV.
The light is activated from the towed vehicle’s brake light switch when the brake is applied.
A single wire is provided with the kit and will need to be routed from the brake light switch to the front of the towed vehicle.
You will need to install a brake light relay kit. This kit will eliminate two problems.
It will disable the towed vehicle from lighting the brake lights thus eliminating a battery run down condition.
It will also keep the braking unit from overriding the turn signals while towing.
The relay kit is available from Roadmaster and included with Blue Ox’s BrakeMaster.
There is a separate wire with quick connectors to attach between the towed vehicle and RV.
A wire will need to be routed from the rear of the RV all the way to the front, then inside to the dash area.
A hole can be drilled to install the light.

A breakaway unit is separate for both braking units and is required by law in some areas.
Unfortunately, the breakaway makes a very simple and easy to install braking unit difficult and complicated.
In my experience the breakaways take about as much time to install as the rest of the system.
The breakaway uses a separate air storage cylinder to supply air to the braking unit in case of a separation from the RV.
There is the typical 2 wire breakaway electrical switch to mount at the front of the towed vehicle.
This switch will be linked to the RV with a small lanyard cable.
You will need to find a location under hood for a rather large air supply tank.
The tank will tee into the air supply line feeding the inside cylinder.
There is a solenoid assembly that activates the breakaway from the breakaway switch.
There is tee to feed the inside cylinder from the solenoid.

This type of air braking systems is what I recommend for RV’s with full air brakes
as long as the manufacturer of the RV permits tapping into the air brakes.
They work proportionately from the RV’s brakes without electronics which makes them very accurate, reliable, and dependable.
Preparing to tow is quick and easy. The only problems I have seen with this system have been with the breakaway.
The air operated breakaway system is reliable with the exception of the breakaway switch which I explained in a previous article.