Lowering trailing axle function

W35.50-1021-09

1 Hydraulic cylinder

2 Trailing axle

3 Lift solenoid valve

4 Lowering solenoid valve

5 Motor

6 Hydraulic pump relay

7 Pressure limiting switch

K18 Check indicator relay

K19 Lowering end shutoff relay

K20 Lowering relay

K21 Lifting end shutoff relay

S95 Lower axle ON switch

S96 Overload switch

8 Nummek axle control module

9 Trailing axle display field

A39 Nummek axle

K14 Starting-off aid time relay

K15 Reclosing lock time relay (France)

K16 Lower time relay

K17 Drop-off delay time relay

The raised trailing axle can be lowered in three different ways.

1. By actuating the lower axle ON switch (S95).

2. Automatically when the drive axle load reaches 13 t.

3. Automatically when the key in the steering lock is turned back from the driving position (longer than 5 seconds).

Function sequence for 1:

Function prerequisites:

 Ignition ON

 Trailing axle raised

If the lower axle ON switch (S95) is pressed down, the switch opens and the power supply is interrupted to input S at the lower time relay (K16).

 The lower time relay, however, remains active for another 60 seconds.

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The lowering solenoid valve (4) is supplied with power via the idle state of the starting-off aid time relay (K14) and lowering end shutoff relay (K19). The lowering relay (K20) simultaneously picks up and supplies power to the hydraulic pump relay (6).

The hydraulic pump relay (6) picks up and switches B+ to the motor (5). The motor drives the pump component of the hydraulic pump in the hydraulics box. The trailing axle (2) is lowered.

The check indicator relay (K18) drops out and the display in the trailing axle display field (9) extinguishes.

The pressure limiting switch (7) closes once the pressure reaches 140 bar (France) or 128 bar (foreign EC). The lowering end shutoff relay (K19) is supplied with power via the diode box V1and switches to self-hold.

As a result the power supply is interrupted to the lowering relay (K20); the lift solenoid valve (3) and the hydraulic pump relay (6) drop out. The motor (5) of the hydraulic pump is switched off.

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Function sequence for 2:

Function prerequisites:

 Ignition: ON

 Drive axle load 13 t.

 Trailing axle raised

When the drive axle load exceeds 13 t, the overload switch (S96) increases its resistance and the self-holding function of the starting-off aid time relay (K14) is no longer active after 85 seconds (France) or 120 seconds (foreign EC).

The trailing axle is lowered in other cases as described for function sequence 1.

Function sequence for 3:

Function prerequisites:

 Ignition: ON

 Trailing axle raised

 Vehicle stationary

1 Switch off ignition.

The power supply to input S at the drop-off delay time relay (K17) is interrupted. After 5 seconds, terminal 30 is switched thus interrupting the power supply to input S at the lower time relay (K16).

 The lower time relay, however, remains active for another 60 seconds.

The trailing axle is lowered in other cases as described for function sequence 1.