In this post I mentioned that before every camping trip I test the trailer’s breakaway switch. I received several questions about this statement and these questions concerned two very important items:
- What is a breakaway switch?
- How do I test a breakaway switch?
How Trailer Brakes Work
Today most travel trailers (to include tent trailers) come with electric brakes. In California every trailer weighing over 1,500 lbs Gross Vehicle Weight is required to have trailer brakes on at least two wheels and the brake system must also have a “breakaway” switch. In addition, all trailers except 5th Wheels must have safety chains. Most states have similar laws.
Electric Brakes
The most common brake system on trailers are electric brakes.
A brake controller inside the tow vehicle is activated when the brake pedal is pushed which sends voltage to the magnets in each wheel with brakes to activate the trailer brakes.
Surge Brakes
Are hydraulic brakes that do not have a brake controller in the tow vehicle. Instead, a pump actuator applies hydraulic pressure to the brakes based on the trailer’s weight and momentum. Today surge brake systems are primarily found on boat trailers because water will damage the electric brake systems used on most trailers. Surge brake systems are more complicated and much more expensive to install and maintain than electric brakes, which is why most camping trailers use electric brakes. Surge brake systems are not necessarily better.
How Breakaway Switches Work
An electric breakaway switch requires an adequate battery mounted on the trailer to apply the brakes.
In the event that the trailer becomes uncoupled from the tow vehicle the breakaway switch will apply the trailer brakes. On an electric brake system, a cable is connected to the tow vehicle and the other end of the cable is connected to the breakaway switch. Should the trailer become uncoupled from the tow vehicle hitch ball, the cable pulls the pin out of the breakaway switch, and the trailer brakes are applied. An electric breakaway switch requires an adequate battery mounted on the trailer to apply the brakes.
Surge brake systems also have breakaway switches, but they do not require a battery to operate.
It is important that the breakaway cable is shorter than the safety chain, but not too short that the pin can be pulled out of the switch if the chain is stretched tight such as in a very sharp turn or when driving over a deep depression in the road.
Testing the Breakaway Switch
This explanation is for an electric switch, but surge systems are usually similar. If you have a surge system, check the Owner’s Manual, contact the manufacturer, or as a last resort use Google.
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- With the trailer and tow vehicle stopped, remove the trailer harness plug from the tow vehicle.
- Pull the pin out of the breakaway switch, this may require a little bit of force… about 35 foot-pounds or more .
- Pull the trailer forward — forward motion is required for the shoes to make contact with the drum force the brake shoes to shoe wedges against the rotating drum while the drum tries to pull the shoe along with it. This motion or action pulls the shoe even more tightly against the drum, increasing the braking force.
- Continue to try to move forward. The trailer should not roll forward freely.If the trailer does easily roll forward, something is wrong with the brake system, and not necessarily the breakaway switch itself.
- If the breakaway test passes, then re-insert the pin into the breakaway switch, and plug the trailer wiring harness back into the tow vehicle’s socket.
If the trailer did not pass the test, the entire system needs to be diagnosed and the trailer should not be towed until the brakes are adjusted or repaired.
Breakaway system parts or even complete systems with a battery are available on Amazon and are fairly inexpensive.