1 Introduction
2
WABCO Maintenance Manual MM-0112 (Revised 07-18)
Figure 1.3
The type of axle determines sensor mounting location.
앫 Steering axle sensors are installed in the steering knuckle or in a
bolted-on bracket.
앫 Drive axle sensors are mounted in a block attached to the axle
housing or in a bolted-on bracket.
Check the wheel speed sensors for correct alignment and
adjustment. Apply lubricant to the sensor and sensor clip whenever
wheel-end maintenance is performed. Make sure tooth wheels are
free of contaminants. Refer to Section 3 and Section 4 for more
information.
Pressure Modulator Valves
A modulator valve controls air pressure to an affected wheel-end
brake during an ABS, RSC or ESC event to reduce speed and
prevent wheel lock up. Modulator valves are also used during ATC
events to properly gain traction on the affected wheel end.
Figure 1.4.
Figure 1.4
A modulator valve is usually located on a frame rail or cross member
near the brake chamber or as part of a valve package. A valve
package combines two modulator valves, a service relay
(Figure 1.5) or quick release valve (Figure 1.6), and depending on
the vehicle configuration, an active braking valve (ABV).
Figure 1.5
Figure 1.6
Easy Listening Tip!
To ensure the ABS valves are working — just listen! Figure 1.7.
Park the vehicle on a level surface. Block the wheels to
prevent the vehicle from moving. Support the vehicle with
safety stands. Do not work under a vehicle supported only by
jacks. Jacks can slip or fall over. Serious personal injury and
damage to components can result.
1. Turn on the ignition.
2. Wait for the ABS indicator lamp to come on.
3. Listen for the valves to click or puff/chuff air in the order shown
in Figure 1.7.
Figure 1.3
Figure 1.4
1002009b
SENSOR
CLIP
SENSOR
TOOTH
WHEEL
BAYONET-STYLE
CONNECTOR
AIR IN
(PORT 1)
AIR OUT
(PORT 2)
4003992b
PRODUCT
IDENTIFICATION TAG
Figure 1.5
Figure 1.6
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
1002011a
472 500 30. 0
MADE IN GERMANY
001 20/98
1003359a
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