Friday, June 2, 2023


Electric brakes — Unintended breakaway switch activation


gary-736Dear Gary,
After we set up our 5th wheel at the RV park, the breakaway switch cable got snagged in the truck box and I pulled the plug out of the breakaway switch. I noticed it laying in the box three days later. I immediately put the plug back in. The trailer is plugged into 50-amp service so the batteries are continuously being charged. Would there be any damage to the brake magnets or the switch itself? Also when would the magnets release — when I reinserted the plugs, or would I need to jack up the trailer and spin the wheels? Your assistance would be appreciated. —Garry F.

Dear Garry,
The good news is that it’s unlikely anything was damaged by the constant, three-day amp draw. I’m sure the magnets got pretty warm, but nothing was spinning so there would be no extra wear on the magnets or the armature plate inside the wheel assembly. As soon as you reinserted the pin, the current flow was terminated. As long as the batteries held their charge by being plugged into shore power the whole time, chances are the batteries are fine too.

Unless the trailer was also plugged into the truck during this time, there’s nothing to worry about from the dash controller end of the circuit. If the truck WAS plugged into the trailer, I’d replace its 12-volt circuit breaker, which may have been rendered weaker due to the constant current flowing through it. That component may have overheated, but typically it would not be involved in activating the brakes under normal breakaway circumstances anyway. You should be good to go!

Read more from Gary Bunzer at the See Gary’s videos about RV repair and maintenance.




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Mel Goddard
6 years ago

If the trailer brakes were ‘on’ for the whole three days, I would bet that the electro-magnets were cooked.
That’s a lot of energy going into the coil, and no airflow to cool them.
I would look into it further, before the trip was resumed.

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