Wiring in break-away switch

[Airwave503]

Maybe this is a dumb question, but please help me out.

The 2 wires coming out of the break-away switch, one connects to the blue trailer brake wire coming from the tow vehicle to the trailer breaks (correct?).

And the other connects to 12V positive, but is it 12V positive coming from the tow vehicle, or the 12V positive from the trailer battery?

I would have thought the trailer battery in the event your chains fail and the 7-pin connector cable comes out you'd still want the trailer brakes to activate....no?

Thanks.
--Jason

[azflycaster]

The switch is wired to the trailer battery for the reason you stated.

[Dingo Girl]

here's a diagram from the forums.

[uncle_bob]

Hi

Often one of the wires on the 7 pin goes straight to the battery. This makes the "what goes where" a bit confusing when you look at it.

Bob

[richard5933]

There are two power leads to the brake system on the trailer.

1) Fed from the TV's harness and which applies the brakes according to the settings on the TV brake controller.

2) Fed from the emergency breakaway switch.

These two feeds both connect to the trailer's brake wiring. All the brakes are connected in parallel. On my trailer there are two blue wires feeding the brakes - one blue wire from the 7-way cable from the TV, and another blue wire from the breakaway switch.

The breakaway switch has two wires. One wire goes to feed the brakes as I described above. The other wire is connected to a 12vdc+ source and where the breakaway switch gets its power. When the cable is pulled and the plug in the switch is removed, the connection between these two wires is made and power is sent from the 12vdc+ source to the brake system.

On my trailer the breakaway switch's 12vdc+ power lead is fed directly from the positive side of the batteries via a self-resetting circuit breaker. This circuit breaker is always connected to the batteries and does not go through the disconnect switch.

Yours might be connected differently so check your manual for the wiring diagram. However you connect it, do it in a way that the breakaway switch has power at all times when you are pulling the trailer regardless of whether or not the TV is still attached. The whole point is to provide braking when the TV and the trailer separate.

[Airwave503]

Thanks all. I was thrown off by my guy down at the U-haul hitch center who insisted that the break-away got it power from the TV and relied on the safety chains holding and keeping the 7 pin connected. I was further confused by some Utubes I found where they said you have to plug the 7 pin into the TV in order to test the break away.

What I'm getting from you guys is that the one wire from the break away splices into the blue wire coming from the 7 pin and going to the trailer brakes. The other wire could get it's 12V either from splicing into the black wire coming from the 7 pin and going to the positive terminal of the trailer battery (the wire that lets the engine charge the battery while towing) -or- it could connect with a separate wire going straight to the trailer battery.

Thanks!

[richard5933]

Originally Posted by Airwave503

Thanks all. I was thrown off by my guy down at the U-haul hitch center who insisted that the break-away got it power from the TV and relied on the safety chains holding and keeping the 7 pin connected. I was further confused by some Utubes I found where they said you have to plug the 7 pin into the TV in order to test the break away.

What I'm getting from you guys is that the one wire from the break away splices into the blue wire coming from the 7 pin and going to the trailer brakes. The other wire could get it's 12V either from splicing into the black wire coming from the 7 pin and going to the positive terminal of the trailer battery (the wire that lets the engine charge the battery while towing) -or- it could connect with a separate wire going straight to the trailer battery.

Thanks!

I think you have it understood, mostly.

The power to the breakaway switch should be separate from the wire on the 7-wire harness though. It should be fed directly from the trailer's batteries so that it has a few possible failure points as possible. On my trailer there is only a self-resetting breaker between. The whole idea is for the brakes to be able to be applied when the 7-wire harness is no longer connected to the TV or even present.

By connecting the breakaway to the 7-wire harness trying you leave open the possibility of not having power supplied to the e-brakes if the TV gets disconnected from the trailer, including if the entire 7-wire umbilical gets ripped out in the process of your trailer breaking free. Catastrophic failures are usually pretty catastrophic after all.