[encantotom]

the air coupling at your hitch is one of two things, but both for towing.

i have a monster hitch on mine because they used it to pull humongo trailers. the air coupling when i got it had constant air pressure on it to be used on the trailer for braking i assume.

i used the M&G braking system, so when i was visiting steve bare, we re plumbed the coupler so it just provided air when the coach brakes are applied.

tom