Breakaway switch.

[Mollysdad]

How does the breakaway switch get power from the house batteries?

[TheGreatleys]

Mine is wired to the DC+ "battery feed" near the umbilical connection (fat black or blue wire) which passes through the fuse box to the house battery.

[Malia20]

On my 2017 FC20 there is a positive bus bar between the battery and the battery switch solenoid. Coming off this buss is a fused black wire that feeds the breakaway switch. In this configuration, the breakaway switch is not turned off by the standard battery switch, so if the battery is good the breakaway will always be ready.

[Mollysdad]

Originally Posted by Malia20

On my 2017 FC20 there is a positive bus bar between the battery and the battery switch solenoid. Coming off this buss is a fused black wire that feeds the breakaway switch. In this configuration, the breakaway switch is not turned off by the standard battery switch, so if the battery is good the breakaway will always be ready.

I see. Thanks.
I knew there wasn't a pair in the battery box, and I've installed a battery disconnect switch on the black or - side. I'll need to keep the battery switch "on" while towing or else the brakes have no emergency power.
I'd do that anyway because with the batteries "off" the tow vehicle won't charge the batteries either.

[uncle_bob]

Hi

The weird thing that *looks* like a DC bus bar actually isn't one. Yes, that *is* a surprise. Instead it's a weird SAE Type II breaker arrangement. It very much does look like a bus bar though doesn't it? The breakaway runs through a breaker to get to the battery. Since it's a thermal / self reset breaker it is very non-obvious that's what they did.

Bob