BENDIX PP-DC User Manual

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Bendix® PP-DC™ Park Control Valve

EXHAUST

SUPPLY 12

SUPPLY 11

SD-03-3619

SUPPLY 11

DELIVERY
21

EXHAUST

COVER

BUTTON

FIGURE 1 - PP-DC™ P ARK CONTROL VAL VE

DESCRIPTION

The Bendix® PP-DC™ park control valve is a push-pull,
manually operable on/off valve. It is dash board-mounted
and provides in-cab control of truck or bus parking brakes.

The valve is pressure sensitive – it automatically moves from
the applied to the exhaust position if total system pressure
drops below 20 to 30 psi. Also, manually pulling the button
will apply the parking brakes.

The PP-DC™ valve body is made of non-metallic, non­corrosive material, and the cover is available in two mounting
variations (see Figure 1). The valve is designed to accept
1/4" P.T. fittings or push-to-connect fittings that use SAE
J844D non-metallic air brake tubing.

Ports:

Port Embossed I.D.
Primary Reservoir Supply Supply 11

Secondary Reservoir Supply Supply 12
Delivery Delivery 21

Exhaust Exhaust 3
Operating pressure: 150 psi max.
Operating temperature: -40° to 200°F

Basic valve weight: Approximately .8 lbs.

BUTTON

OPERATION

GENERAL

The PP-DC™ valve receives its supply of air from the primary
service reservoir or the secondary service reservoir, whichever
is at the higher pressure. When the button is pushed in, the
valve delivers air to the spring brake chambers (usually
through a spring brake valve such as the Bendix® SR-1
valve and a relay or quick release valve). The air releases
the spring brakes for normal vehicle operation.

T o apply the parking brakes, the button is pulled out, which
exhausts the PP-DC™ valve delivery and releases air from
the spring brake chambers.

If total system pressure drops below 20 to 30 psi, the valve
will automatically “pop out,” which removes the hold-off air
in the chambers and applies the spring brakes.

P ARKING BRAKES RELEASED

T o release the parking brakes, the push-pull button is pushed
in. The PP-DC™ valve plunger moves, closing the exhaust
port with the exhaust seal and allowing the plunger o-ring to
move past the guide spool. Supply air then travels out the
delivery port to release the brakes.

Note that Figure 3 shows the primary service reservoir
supplying the PP-DC™ valve. The double check valve
diaphragm has sealed the secondary reservoir supply port
and allows air to pass from the primary reservoir into the
PP-DC™ valve.

™

1

™

PP-DC

VALVE

SUPPLY (PRIMARY

RESERVOIR)

SUPPLY (SECONDARY

RESERVOIR)

DEL.

SR-1™ SPRING
BRAKE VALVE

EXH.

ANTI-CMPD.

LINE

FIGURE 2 - TYPICAL 4 X 2 TRUCK SCHEMATIC WITH PP-DC™ PARK CONTROL V ALVE

If primary service reservoir pressure drops below secondary
service reservoir pressure, the double check valve reacts as
shown in Figure 4. It seals the primary service reservoir
supply port and supplies the PP-DC™ valve with air from the
secondary service reservoir. As is shown, the push-pull button
remains in and the spring brakes remain released.

removed. Where circumstances require that the
engine be in operation, EXTREME CAUTION should
be used to prevent personal injury resulting from
contact with moving, rotating, leaking, heated or
electrically charged components.

3. Do not attempt to install, remove, disassemble or
assemble a component until you have read and

P ARKING BRAKES APPLIED

Figure 5 shows the PP-DC™ valve in the parking-brakes­applied position. This will occur if the driver manually pulls
out the push-pull button or if total system pressure drops to
below 20 to 30 psi.

When the button “pops out,” the exhaust seal moves to
open the exhaust port to atmosphere, allowing delivery line
pressure to exhaust. The plunger o-ring moves to seal off
supply pressure. Spring brake hold-off air is exhausted
through the spring brake relay valve.

thoroughly understand the recommended
procedures. Use only the proper tools and observe
all precautions pertaining to use of those tools.

4. If the work is being performed on the vehicle’s air
brake system, or any auxiliary pressurized air
systems, make certain to drain the air pressure from
all reservoirs before beginning ANY work on the
vehicle. If the vehicle is equipped with an AD-IS
air dryer system or a dryer reservoir module, be
sure to drain the purge reservoir .

5. Following the vehicle manufacturer’s
recommended procedures, deactivate the electrical

WARNING! PLEASE READ AND FOLLOW
THESE INSTRUCTIONS TO AVOID
PERSONAL INJURY OR DEATH:

When working on or around a vehicle, the following
general precautions should be observed at all times.

1. Park the vehicle on a level surface, apply the
parking brakes, and always block the wheels.
Always wear safety glasses.

2. Stop the engine and remove ignition key when
working under or around the vehicle. When
working in the engine compartment, the engine
should be shut off and the ignition key should be

system in a manner that safely removes all
electrical power from the vehicle.

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® replacement parts,
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.

SERVICE

RELAY VALVE

QR-1C

VALVE

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