Iveco Stralis AT/AD. Manual - part 257

Figure 47

73915

The duplex control valve generates electric and pneumatic
signals needed to control the brake system.
Under normal circumstances the component works with the
electric circuit only, while the pneumatic circuit is activated
when the electric circuit is out of service.

Figure 48

73914

It takes air from the tanks and distributes it to the braking
elements.
It is self-limited, that is it limits the delivery of air at a set
maximum pressure, the outcome of which is a greater
availability of energy and a constant maximum braking
pressure irrespective of the pressure swings in the tanks.
Vehicles fitted out as trucks have duplex control valves
mounted with the function of correcting the braking force of
the operator elements of the front axle according to the
correction made by the load apportioning valve.

793110

Duplex control valve
(vehicles without EBS)

Duplex control valve with electric transmitter
(vehicles with EBS)

TRALIS

AT/AD

AIR SYSTEM - BRAKES

Base - January 2003

TROUBLE

POSSIBLE CAUSE

REMEDY

Air leaks from the outlet
hole

Leaks from the outlet pipes due to wear of the
gaskets

Overhaul the device, replacing the worn parts.

Control valve with abnormal
self-limitation

Self-limitation higher or lower than as required Set the device using the specific screw.

Vibration during braking

Spring wear

Overhaul the device, replacing the worn parts.

Air leakage due to piston gaskets in the two
sections

Overhaul the device, replacing the worn parts.

Abnormal operation of the
brake light switch

It fails to close the electric circuit

Replace the switch.

It fails to open the electric circuit

Replace the switch.

Figure 49

The device allows to speed up compressed air release from

combined cylinder section, so cutting down braking time.

793331

Relay valve (vehicles without EBS)

Proportional relay valve for front axle

(vehicles with EBS)

73916

This component modulates the pressure to the cylinders of

the front axle.

It comprises a proportional solenoid valve, a pneumatic relay

and a pressure sensor.

Figure 50

36743

52871

The version for the "Graduated" pipe is equipped with a red

cover and a safety projection (1), while the version for the

"Automatic" pipe is equipped with a yellow cover and a side

safety projection (2). The safety projections are used to avoid

coupling errors.

Figure 51

798510

Coupling heads

AIR SYSTEM - BRAKES

TRALIS

AT/AD

Fault Diagnosis (vehicles without EBS)

TROUBLE

POSSIBLE CAUSE

REMEDY

Air leaks from the outlet

with the control pipe

exhausting

Leakage from the introduction or from the seals. Overhaul the device, replacing any defective parts.

Air leaks from the outlet

with supply in the control

pipe

Leakage from the piston gasket or from the exĆ

haust valve.

Overhaul the device, replacing any defective parts.

Figure 52

Figure 53

73917

Its task is to modulate the pressure to the brake cylinders of
the rear axle.
It has an electronic control unit that controls the rear speed
sensors and the wear of the brake linings of the rear axle.
This electronic control unit communicates over the CAN
network with the E.B.S. control unit.

60934

A = Diagram of rear axle electro-pneumatic modulator (for

4x2 and 6x2 truck versions).

B = Diagram of rear axle electro-pneumatic modulator (for

tractor versions).

TRALIS

AT/AD

AIR SYSTEM - BRAKES

Base - January 2003

Fault Diagnosis

TROUBLE

POSSIBLE CAUSE

REMEDY

Air leaks from the outlet
with the control valve lever
in the brake release position

Piston, outlet valve, seals worn or defective.

Clean thoroughly, check the rubber parts and the seats are
sound.

Air leaks from the outlet
with the control valve lever
in the emergency or parking
braking position

Piston and associated seal defective or deterio-
rated.

Clean thoroughly, check the parts and overhaul the device,
replacing the defective parts.

Air leaks from the cover
of the control valve lever

Plate, gasket, seals worn.

Clean the parts thoroughly, check the surfaces of the
gasket and seals, check the integrity of the rubber parts and
the relevant seats. Overhaul the device, replacing the de-
fective or worn parts, and restore the mating faces if
necessary.

Control valve lever hard
to turn

Interference inside the control valve.

Clean thoroughly and check all the component parts.
Overhaul the device, replacing defective parts. During as-
sembly, grease all the sliding parts in moderation.

If you find any defects or wear such as to jeopardize oper-
ation, replace the complete device.

On vehicles with an ABS/EBL system, this component has the
task of sending the rear axle braking control relay valve the
control pressure from the duplex control valve (normal
working function). With the ASR function active, this
component will send the activation pressure from the ASR
solenoid valve. In addition, it is used on 6x2 vehicles to
transmit the pressure in the air springs, to the added axle
braking control relay valve, according to the load. On vehicles
with the EBS, it has the task of sending the pressure of the
front axle braking relay valves according to the load bearing
on the air springs of the added axle.

73918

35805

73919

33986

Figure 54

This component has the task of ensuring the rear axles brake
even if the EBS is entirely out of service.

ABS-EBS solenoid valve

This component modulates the air pressure in the brake
circuits. When the electronic control unit detects a tendency
for one of the wheels to lock, the valve shuts off the supply
to the brake cylinder, preventing the wheel from locking.

Redundancy valve (for 4x2 and 6x2 trucks)

Dual stop valve

Figure 55

793332

Triple servo control valve
(vehicles without EBS)

Figure 56

Figure 57

The device controlled by the two independent circuits of the
duplex control valve and the spring brake circuit of the tractor
controls trailer braking.
It incorporates a device making it possible to brake the trailer
even in the event of control pipe failure.

AIR SYSTEM - BRAKES

TRALIS

AT/AD

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