Fan switched - function

W20.50-1005-09

Shown on vehicle with preinstallation for semitrailer hydraulic

1.1 Hydraulic pump for oil cooler

1.2 Hydraulic pump for semitrailer hydraulics

2 Oil reservoir

2.1 Oil level indicator

2.2 Floor valve

2.3 Oil drain screw

2.4 Oil filler cap

2.5 Filler strainer

3 Oil filter housing

3.1 Pressure gage for service indicator

3.2 Air admission/release valve

3.3 Wastegate

4 Heat exchanger

5 Fan motor

B66.1 Retarder oil temperature sensor (display instrument for oil temperature)

F2-A27 Oil cooler fuse

H35 Display instrument for oil temperature (special equipment)

K1-A37 Oil cooler relay

S115 Transmission oil cooling temperature switch

A High pressure

B Return flow

C Leak oil

D Bypass circuit

6 Suction valve

7 Three-way flow control valve

7.1 Pressure limiting valve (variable)

7.2 Flow limiting valve (variable)

7.3 Measuring connection "Z"

7.5 Oil cooler solenoid valve

8 Oil reservoir

9.1 Pressure line to three-way flow regulating valve (semitrailer)

9.2 Return line from three-way flow regulating valve (semitrailer)

9.3 Return line from the pipeline coupling (semitrailer)

Operating condition: engine run, oil temperature in oil circuit for transmission/ torque converter clutch above the shift point of the transmission oil cooling temperature switch

The transmission oil cooling temperature switch (S115) detects the current oil temperature in the oil circuit for transmission/ torque converter clutch.

From an oil temperature of about 68°C (was 75°C until 31.12.2000) the transmission oil cooling temperature switch (S115) does not emit a signal to the oil cooler relay (K1-A37).

The oil cooler relay (K1-A37) interrupts the current supply to the solenoid valve on the oil cooler (7.5). This blocks the solenoid valve on the return line to the oil reservoir (2) for the oil cooler (7.5).

The oil pressure coming from the oil cooler hydraulic pump (1.1) is passed through the flow limiting valve (7.2) in the three-way flow control valve (7) to the fan motor (5).

The max. oil pressure to the fan motor (5) is limited by the pressure limiting valve (7.1).

This produces the maximum fan speed of 1950 rpm (was 1600 rpm up to 31.3.2000).

The excess oil is led through the throttle in the flow limiting valve (7.2) and over the oil filter to the oil reservoir (2).

If the oil pressure rises above the pressure set at the pressure limiting valve (7.1), the pressure limiting valve (7.1) opens and the excess hydraulic oil flows back through the oil filter (3) to the oil reservoir (2).

The leak oil present in the fan motor (5), flows back along a separate return flow line unpressurized to the oil reservoir.

If the hydraulic fan motor (5) is switched off by the oil cooler solenoid valve (7.5) the replenishing valve (6) prevents the fan motor (5) from stopping abruptly. This avoids damaging the fan motor (5).