Thermal Protection Function - Mercedes-Benz OM 471 Introduction Into Service Manual

Introduction of engine om 471 and exhaust aftertreatment

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i The fan clutch solenoid valve (Y616) is swivel mounted along

with the fan rpm sensor (Y616 b1) on the stub shaft (12). The hose

fitted to the electrical line (15) is used as a torque support. This

prevents the assembly from also turning.

Function

Power is transmitted between the primary side (clutch plate (7))

and the secondary side, consisting of the lid (6) and the housing

(10), through silicone oil shearing in the working chamber.

i Shearing is understood to refer to the displacement of silicone

oil between the drive slats of the clutch plate (7) and the power

take>off slats of the housing (10) and the lid (6).

The rotational speed of the primary side on vehicles without a

high>speed fan drive matches the current engine speed.

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

If the fan clutch solenoid valve (Y616) is not actuated, the oil feed

bore (9) is open and the clutch plate (7) is flushed with the

maximum possible volume of silicone oil.

In other words, the fan wheel (1) rotates at the current engine

speed or the rotational speed that matches the belt drive's step>

up ratio.

The engine management (MCM) control unit (A4) energizes the

fan clutch solenoid valve (Y616) using a pulse width modulated

signal (PWM signal) corresponding to the current cooling

requirement. A magnetic field is generated at the valve lever (4)

which then closes the valve lever (4).

The silicone oil then flows partly or completely through the return

hole (3) back into the working chamber, which then results in the

fan speed being reduced. If the rotational speed of the fan wheel

(1) is to be increased, the PWM signal for actuating the fan clutch

solenoid valve (Y616) is changed accordingly. The magnetic field is

then reduced and the valve lever (4) opens the inflow into the

working chamber.

Introduction of engine OM 471 and exhaust aftertreatment > 09/2011 >

– This printout will not be recorded by the update service. Status: 09 / 2011 –

System components

On vehicles equipped with a high>speed fan drive, the rotational

speed of the primary side is higher by the respective step>up ratio.

i Information on the respective step>up ratio for the belt drive is

stored in the engine management (MCM) control unit (A4).

The secondary side is connected to the fan wheel (1). The main

bearing (14) separates it from the primary side.

The rotational speed of the secondary side is sensed by the engine

management (MCM) control unit (A4) through the fan rpm sensor

(Y616 b1).

The rotation of the primary side generates a centrifugal pressure.

The centrifugal force induces the silicone oil to flow from the

reservoir chamber (5) through the oil feed bore (9) and into the

working chamber. The inflow of silicone oil is regulated by the

valve lever (4). It opens and closes the oil feed bore (9).

The valve lever (4) is actuated by the engine management (MCM)

control unit (A4) through the fan clutch solenoid valve (Y616).

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

This then increases the volume of silicone oil that flows in. The fan

rotational speed and the cooling output are increased. Due to this

operating principle, the electromagnetic viscous coupling (2)

operates in fail>safe mode. In other words, in the event of an

electronic defect, e.g. line break, the electromagnetic viscous

coupling (2) is activated at full output (max. cooling output).