Ford F-650 2015 Owner's Manual page 148

Trailer Charge
B
A
If both knobs are out, and you want to recharge the trailer while leaving
the tractor spring brakes applied, the trailer air supply (A) can be
pushed in to recharge the trailer air supply line. You can also use this
mode to park a combination vehicle with tractor spring brakes.
Automatic Application
If both knobs are pushed in and the brake system air pressure is reduced
to approximately 35 psi (249 kPa), the trailer air supply (A) knob
automatically pops out applying the emergency or parking brakes on the
trailer. If the trailer air supply (A) knob is manually held in and the air
pressure is reduced to approximately 30 psi (207 kPa), a tripper piston
within the valve moves, exhausting the trailer air supply, applying the
trailer brakes. Further reduction of air pressure, while holding the trailer
air supply knob in, causes the parking brake knob to pop out at 25 psi
(172 kPa).
2015 F-650/750 (f67)
Owners Guide gf (ownloose), 1st Printing, December 2013
Canadian_French (fr_can)
Brakes
B
A
B
A
I n f o r ma t i o n P r o v i d e d b y :
147