Relay Valve Operation Modes - BENDIX A-18 TRAILER ABS Manual

6. Never exceed manufacturer's recommended
pressures.
7. Never connect or disconnect a hose or line
containing pressure; it may whip. Never remove a
component or plug unless you are certain all
system pressure has been depleted.
8. Use only genuine Bendix
components and kits. Replacement hardware,
tubing, hose, fittings, etc. must be of equivalent
size, type and strength as original equipment and
be designed specifically for such applications and
systems.
9. Components with stripped threads or damaged
parts should be replaced rather than repaired. Do
not attempt repairs requiring machining or welding
unless specifically stated and approved by the
vehicle and component manufacturer.
10. Prior to returning the vehicle to service, make
certain all components and systems are restored
to their proper operating condition.
Hold
Solenoid
Control
Sleeve
Outlet
FIGURE 11 - Normal Apply and ABS Apply
Control
Outlet
FIGURE 13 - ABS Hold
® replacement parts,
Release
Solenoid
Piston
Supply
Supply
Exhaust

Relay Valve Operation Modes

1. Apply–Treadle pressure is applied to the top of the
piston. The sleeve is depressed until the outlet pressure
matches the pressure at the top of the piston.
2. Normal Release–Pressure at the top of the piston is
vented through the treadle valve. The sleeve rises to
block the inlet while allowing the chamber air to exhaust
through the center of the sleeve.
3. ABS Hold–Hold solenoid blocks treadle pressure. The
piston stabilizes, holding the chamber pressure at the
same level as that which is above the piston.
4. ABS Release–The release solenoid vents air at the top
of the piston while blocking treadle pressure. The sleeve
rises to block the inlet while allowing the chamber air to
exhaust through the center of the sleeve.
Control
Outlet
FIGURE 12 - Normal Release
Control
Outlet
FIGURE 14 - ABS Release
Supply
Exhaust
Supply
Exhaust
13