Safety Features
If the Red ‘Supply’ line breaks or disconnects (and there is pressure in the trailer reservoir), the Relay Emergency valve will apply the trailer brakes automatically (i.e. Failsafe operation). Always check this happens whenever the trailer is unhitched from the tractor.
If the tractor’s braking system fails (or the engine stalls), the driver can still apply the trailer brakes using the tractor’s Secondary brake control (either the foot brake, the Parking brake or an Emergency brake control).
Important Do’s and Don’ts
When coupling / uncoupling, to keep the trailer brakes applied for as long as possible, ALWAYS disconnect the Red line first (before the Yellow line) and re-connect it last.
ALWAYS apply the mechanical Parking Brake. Don’t rely on trailer air reservoir pressure to keep the brakes of an unhitched trailer applied.
NEVER connect both hydraulic and air brakes at the same time. Use either one system OR the other.
ALWAYS ensure the Shunt valve releases when the air brakes are next connected: otherwise, the trailer’s reservoir won’t refill and you will have no trailer brakes!
