Bendix Commercial Vehicle Systems TW-N User Manual

®

Bendix® TW-N™ Two Way Control Valve

MOUNTING

HOLE (4)

EXHAUST

.26” O.D.
(6.6 MM)

DELIVERY

PORT

1/8” P.T.

SD-03-3672

LEVER

LEVER PIN

BODY

PLUNGER

O-RING (LARGE)

SPRING

O-RING (SMALL)

DELIVERY

PORT

SUPPLY

PORT

1/8” P.T.

DESCRIPTION

The TW-N™ valve is a manually operated two position control
valve. It is normally dash or panel mounted and incorporates
a manually operated control lever. The TW-N™ valve was
designed for use as a control for non-modulating air system
devices.

With the exception of the plunger return spring, lever pin
and lever reinforcement the TW-N™ valve is constructed of
nonmetallic material.

The single supply port and delivery port are both tapped with
a 1/8" female pipe thread to accommodate air connections.
A single .26" (6.6 mm) O.D., unthreaded exhaust nipple is
located on the side and midway down the valve body. Each
port is identified with embossed letters; SUP for supply,
DEL for delivery and EXH for the exhaust.

SUPPLY

PORT

FIGURE 1

The TW-N™ valve is generally mounted using two of the four
mounting holes that are provided. All four mounting holes
are tapped with a 10-24 thread.

The TW-N™ valve is interchangeable with the TW-1™ two-way
control valve with respect to vehicle fit and function. Dial
plates and attaching screws can be used interchangeably
on either the TW-N™ and TW-1™ valves, however other detail
components are not interchangeable.

OPERATION

With the TW-N™ valve in the exhaust position, air at the
supply port is prevented from flowing to the delivery port by
the lower o-ring on the plunger. (Figure 2) When the lever is
moved to the delivery position, (Figure 3) the return spring
and air pressure moves the plunger allowing the lower plunger
o-ring to slide past the delivery port passage. With the plunger
in this position (Figure 3), air flows from the supply port and
out the delivery port.

1

EXHAUST

EXHAUST

DELIVERY

PORT

SUPPLY PORT

EXHAUST POSITION

FIGURE 2 FIGURE 3

Moving the lever to the exhaust position, forces the plunger
toward the supply port, causing the lower plunger o-ring to
slide past the delivery port passage sealing the supply from
the delivery. Air at the delivery flows through the valve body,
around the plunger and out the exhaust.

PREVENTIVE MAINTENANCE

Important: Review the Bendix Warranty Policy before

performing any intrusive maintenance procedures. A warranty
may be voided if intrusive maintenance is performed during
the warranty period.

No two vehicles operate under identical conditions, as a
result, maintenance intervals may vary. Experience is a
valuable guide in determining the best maintenance interval
for air brake system components. At a minimum, the TW-N
valve should be inspected every 6 months or 1500 operating

2. With the TW-N™ valve in the exhaust position apply a
soap solution to the exhaust. Leakage should not exceed
a 1" (25.4 mm) bubble in 5 seconds or less.

3. With the TW-N™ valve in the air delivery position apply a
soap solution to the exhaust and around the plunger.
Leakage should not exceed a 1" (25.4 mm) bubble in 5
seconds or less.

If the TW-N™ valve does not function as described or leaks
excessively, it should be replaced or repaired using a
genuine Bendix maintenance kit available at authorized
Bendix parts outlets.

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.

hours, whichever comes first, for proper operation. Should
the TW-N™ valve not meet the elements of the operational
tests noted in this document, further investigation and service
of the valve may be required.

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

OPERATION AND LEAKAGE TESTS

1. With vehicle air pressure at governor cut-out and the
engine turned off, place the TW-N™ valve control lever in
the air delivery position. Note that the device being
controlled promptly responds. Place the control lever in
the air exhaust position and note that air is promptly
and completely exhausted from the TW-N™ valve.

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

DELIVERY

PORT

SUPPLY PORT

DELIVERY POSITION

2