Fan not switched - function

W20.50-1006-09

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

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.

Below 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 relay oil cooler (K1-A37) actuates the oil cooler solenoid valve (7.5) an. This opens the solenoid valve on the return line to the oil reservoir (2) for the oil cooler (7.5).

The oil pressure from the oil cooler hydraulic pump (1.1) is passed through the throttle in the flow limiting valve (7.2) and the opened oil cooler solenoid valve (7.5) to the oil reservoir (2). The hydraulic fan motor (5) is not switched on.

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