Bill,

I think your coach has 12 volt brake lights. As Kevin points out a relay should be used so you do not load the brake light circuit more than its wiring or CB will handle, and the power source for the trailer brake controller and thus the trailer brakes can come from the 12 volt post in the big electrical box over the engine. You can pick up the 12 volts directly from the coach brake light circuit, but if you prefer you can also pick it up from the toad brake light wiring receptacle.

I think only early 90s vintage or maybe earlier coaches had 24 volt coach lighting (except for headlights which always were 12 volts).