DAF LF45, LF55 Series. Manual — part 459

©

200436

2-15

Inspection and adjustment

BRAKE SYSTEM AND COMPONENTS

ΛΦ45/55 series

6

4

2.10 CHECK AND ADJUST INPUT AND OUTPUT PRESSURES OF THE AIR

SUPPLY UNIT

Inspecting the cut-out pressure
1.

Connect a pressure gauge to the central

drain/filler connection.

2.

Pressurise the air system.

3.

Check that the pressure regulator cuts out at

the correct reading.

4.

If this is not the case, adjust the value using

the screw on the air dryer (see arrow) as

follows:

Adjusting the cut-out pressure
1.

If the cut-out pressure is too low, tighten the

adjusting screw a little so that the cut-out

pressure becomes too high.

2.

Ensure that the pressure regulator is

switched on. If it is switched off, let some air

escape through a reservoir until the system

pressure falls beneath the cut-in pressure.

3.

Pressurise the air system to a little over 10

bar.

4.

Unscrew the adjusting screw until the

pressure regulator cuts out (see "Technical

data").

5.

Check the cut-out pressure in the way

mentioned above (see "Technical data").

Adjusting trailer vehicle system pressure
1.

Fit a pressure gauge to the trailer supply

connection (red connection).

2.

Build up pressure in the brake system (air

dryer should blow off).

3.

Check the pressure (see "Technical data").

4.

If necessary, adjust the pressure by turning

the adjusting screw.

R600480

R600652

BRAKE SYSTEM AND COMPONENTS

2-16

©

200436

Inspection and adjustment

4

ΛΦ45/55 series

6

2.11 CHECK AIR DRYER REGENERATION FUNCTION IN THE AIR SUPPLY UNIT

Air dryer regeneration function
1.

Pressurise the air system (pressure

regulator should cut out).

2.

Switch the engine off.

3.

The regeneration air should escape via the

vent opening of the air dryer, for

approximately 20 seconds.

©

200436

2-17

Inspection and adjustment

BRAKE SYSTEM AND COMPONENTS

ΛΦ45/55 series

6

4

2.12 CHECK THE 4-CIRCUIT SECURITY VALVE OF THE AIR SUPPLY UNIT

Check pressure build-up on circuits 1, 2, 3
and 4
1.

Lower the pressure in the system to 0 bar.

2.

Connect pressure gauges to circuits 1, 2, 3

and 4.

3.

Pressurise the circuits using the compressor

(engine speed approx. 1000 rpm).

4.

The pressure in circuits 1, 2 and 4 will

gradually increase. Once the opening

pressure of circuit 3 has been reached (see

"Technical Data"), the pressure in circuit 3

will increase.

5.

If no more pressure builds up (cut-out

pressure reached), the supply pressure in

circuits 1, 2, 3 and 4 must meet the stipulated

value (see "Technical Data".

Checking circuit 1
1.

Turn off the engine and simulate a leak in

circuit 1.

2.

The pressure in circuit 2 and 4 may not fall

below the specified closing pressure of

circuit 1. See "Technical data".

Checking circuit 2
1.

Make sure the leak in circuit 1 is remedied

and pressurise the system again.

2.

Turn off the engine and simulate a leak in

circuit 2.

3.

The pressure in circuit 1 and 4 may not fall

below the specified closing pressure of

circuit 2. See "Technical data".

Checking circuit 3
1.

Make sure the leak in circuit 2 is remedied

and pressurise the system again.

2.

Turn off the engine and simulate a leak in

circuit 3 for the trailer circuit (connection

point 23).

3.

The pressure in circuit 1.2 and 4 may not fall

below the specified closing pressure of

circuit 3. See "Technical data".

4.

The pressure in circuit 3 for the parking brake

circuit (connection point 25) must remain

secured by the check valve.

Checking circuit 4
1.

Make sure the leak in circuit 3 is remedied

and pressurise the system again.

2.

Turn off the engine and simulate a leak in

circuit 4.

3.

The pressure in circuit 1 and 2 may not fall

below the specified closing pressure of

circuit 4. See "Technical data".

BRAKE SYSTEM AND COMPONENTS

2-18

©

200436

Inspection and adjustment

4

ΛΦ45/55 series

6

Checking circuit 3 flow-back function
1.

Make sure the leak in circuit 4 is remedied

and pressurise the system again.

2.

Turn off the engine and simulate a leak in

circuit 1.

3.

The pressure in circuit 3 for the trailer circuit

(connection point 23) will decrease to 0 bar

when the pressure in circuit 1 has reached

the activation pressure for the flow-back

function. See "Technical data".