Lowering trailing axle, function

W35.50-1023-09

1 Hydraulic cylinder

2 Trailing axle

3 Lift solenoid valve

4 Lowering solenoid valve

5 Motor

A39 Nummek axle

K18 Check indicator relay

K22 End shut-off relay

K23 Lift-lower relay

S97 Lift/lower axle switch

6 Hydraulic pump relay

7 Pressure limiting switch

8 Nummek axle control module

9 Trailing axle display field

The raised trailing axle can be lowered by actuating the lift/lower axle switch (S97).

Function sequence

Function prerequisites:

 Ignition: ON

 Trailing axle raised

When the ignition is switched on, power is supplied to the lift/lower axle switch (S97).

If the lift/lower axle switch (S97) is pressed down, the switch closes and power is supplied to the lowering solenoid valve (4) and at the end shut-off relay (K22), lift-lower relay (K23) and hydraulic pump relay (6).

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

The lift-lower relay (K23) picks up and grounds the lowering solenoid valve (4) and the hydraulic pump relay (6) via the NC contact of the end shut-off relay (K22). Both the lowering solenoid valve and hydraulic pump relay pick up.

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

When the pressure in the hydraulic cylinder (1) reaches approx. 140 bar, the pressure limiting switch (7) grounds the end shut-off relay (K22). The relay picks up and remains in self-hold. As a result, the grounding of the lowering solenoid valve (4) and hydraulic pump relay (6) is interrupted causing both to drop out. The motor of the hydraulic pump is switched off.