5th plug, surge brakes, etc.

[tonyjh63]

I wrote to my trailer's manufacturer for some info on it, and here is part of the reply:
"Your trailer has "surge" brakes, the 5th wire is for backing up and is connected to your tow vehicle's back-up lights. When you put your tow vehicle in reverse power is sent to a solenoid behind your trailer's master cylinder that by-passes the fluid back into the master cylinder reservoir."
Could someone explain all this to me? Specially that last sentence? Thanks!

 

[fhhuber]

The trailer has a mechanically operated brake system. When the trailer tries to pass the tow vehicle it compresses a spring and actuates the brake cylinder, applying the brakes. The reverse lights being actuated, if you hook the wires up correctly, will actuate a solenoid valve which disables the trailer brakes, allowing you to back up somewhere other than down the boat ramp. Without that valve, attempting to back and go uphill would lock the trailer wheels.

Essentially said the same thing as your manual, just using different words.

Note... the trailer brakes you have will not help AT ALL EVER when backing down the boat ramp...

 

[tonyjh63]

Hey fhhuber, thanks for clearing that up for me!