E5020 Engine cooling

Description

The engine radiator and air conditioner condenser cooling system consists of one fan operated at two different speeds.

• the first speed is activated at a first coolant temperature level or at a certain air conditioner coolant pressure.
• the second speed cuts in at a higher temperature or pressure threshold.

The fan is operated by two specific relays located in the engine compartment unit.

The fan supply line is protected by two specific fuses, located in the engine compartment unit.

The fan can only be switched on when the ignition is ON.

Description of operation

The relays T6 and T7 in the engine compartment unit B1 manage the switching on of the fan N11 at two speeds: their coils are supplied by the ignition-controlled line (15/54), while the power lines are protected by the fuses F6 and F7, of the engine compartment unit B1.

Both are energized by a control signal - earth - coming from the engine control unit M10.

If the engine coolant reaches a first temperature level, or the 4-stage pressure switch K10 indicates to the control unit M10 - pin 9 of connector A - that a first pressure level has been reached, the control unit M10 sends a signal - from pin 50 of connector A - to the fan 1st speed relay, which then sends the supply to the fan N11 via the additional resistor O10: the fan thus turns at the first speed (slow).

If the coolant reaches a higher temperature level, or the 4-stage pressure switch K10 indicates to the control unit M10 - pin 41 of connector A - that a higher pressure has been reached, the control unit M10 sends a signal - from pin 62 of connector A - to the fan 2nd speed relay T7, which sends the supply directly to the fan N11: the fan then turns at the maximum speed.

Wiring diagram

Components

Component location