How is the Breakaway brake light circuit activated (closed). Is a switch activated by the brake pedal travel or a pressure switch in the hydraulic brake system (air over hydraulics), or something else? And where might the switch be found? Thanks for your thoughts.

When Richard Muise had brake light trouble at the Minnesnowta GTG, I believe the switch was located in front under the driver at or near the master cylinder. I think it was in the line rather than on the master itself.

Hopefully a Breakaway owner can give you a more precise location. good luck.

Thanks Steve. I have to confess. My brake lights function properly. I would like to be able to occasionally activate my brake lights without having to depress the brake pedal - for safety purposes. Maybe others have had experienced such an instance. Or maybe to express gratitude to a thoughtful driver. You know, hang with the big rigs.

I thought I could install an independent 12V power source into the circuit, after the stock switch. The independent power source would be controlled with a momentary, normally open spring returned switch.

Might be easier than you think. Often the brake circuit is hot all the time and the brake switch just grounds the circuit. You may be able to tie a wire to the hot side and ground it through another switch near the driver seat.

It’s called the emergency flasher switch.

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and ground it through another switch

My juvenile knowledge of electricity always envisions switching power in. Will post switch location when found. Thanks,
Sparks

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Or maybe to express gratitude to a thoughtful driver. You know, hang with the big rigs.

Why not just blink the parking lights or briefly the four ways?

I believe Mr Darryl showed me a button on his Breakaway that would flash the rear tail lights and running lights .

There is a pair of switches mounted to the foot peddle air system. Those switches closes to ground thru air actuation.

On the dash there is a running lite switch that is a momentary switch so you can signal "thank you" when you pass a truck that has flashed his lights to signal you are OK to come back into the lane.

The switches located at the air/hydraulic master cylinders are for warning if the master cylinder moves to far to the end of the stroke which would cause loss of braking.

Any actuation of the brake or running lights will also result in the cruise control shutting off.

Great point inre. the cruise control deactivation.

My understanding of the dash running light switch is it deactivates all lights, except head lights. Lights would have to be on for purpose to be served. Please correct me if I am wrong.

The warning switches/lights associated with the master cylinder piston travel would not be the switches I am looking for. I am looking for the switch which closes the circuit for the rear brake lights.

Just looking for a project of my own. This quarantine "to do" list is ridiculous.

Yes, you are correct, running lights must be on for the dash interrupter to work.

Below the brake peddle there is a trundle valve to operate the air actuators on the master cylinders. Two larger airlines attach to the trundle valve on the passengers side. Two airlines come off the valve on the driver side smaller than the one just mentioned, red and green. Very close to these line connection to the trundle valve you will see the air operated switches, kinda hard to get to bu not impossible. These are closure to ground switches.

Many times the connections to these switches get loose or corroded which cause brake light failure.

MWrench, I am so thankful you own a Breakaway. No wonder I couldn't locate the switch(s). I will try to post a picture of my final set up.

"MWrench, I am so thankful you own a Breakaway. "

Me too ! Mr Ed is a wealth of information

Switch(s) location is near the steering column (blue) passing through floor board.

As MWrench described, there are two pressure activated switches. It appears to me this setup results in the brake lights activating when the air pressurizes either of the two brake circuits. The electrical circuit closes when either switch is pressurized. Please correct me if I am wrong.

I plan to simply jump the terminals on either switch and include a normally open switch mounted conveniently for the driver.

It might work fine , just have to make sure it doesn't deactivate the cruise control