Two vs three wire breakaway switches

[Dougeye]

One to the battery, one to the trailer brake wire, and in the case of a three wire switch, one to ground. Why the difference? Are two wire switches grounded through the mounting plate?

 

[Birdhunter1]

A switch doesn't have to ground, hence one wire from the charge battery and one to the brakes on a two wire. On most trailers I have worked on this is what it has, pretty simple and durable.

I don't know why grounding the switch would make a difference but it could be another ground in the system so if you are running a two wire cable to the axle and have to cut it to splice into the supply wire to the brakes you could splice the ground of the brake cable together AND ground it again at the switch. (But I could be wrong on this too and there may be another purpose for the third wire.)

 

[Dftodd]

I found the diagram. But it depends on the switch. Most have 1 wire to battery, 1 to brakes, 1 wire is a ground.

I always just install the two wire brake away controller. It's a much easier and cleaner install. Just connect 1 wire to battery. And splice the other wire into the brake wire coming from the plug going to the electric brakes.


Here's a screen shot from the Etrailer page.View attachment 661947

 

[Dougeye]

Solved. The switch itself isn't grounded, the ground wire is on switches that have an LED that comes on when the switch is activated. The two wire switches don't have the LED.

 

[Birdhunter1]

That makes sense