Radiator fan (B235R, B205L/R)
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Radiator fan (B235R, B205L/R)
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Generation IV engines (B235R, B205L/R) are fitted with a radiator fan to keep the coolant within certain temperature limits. The radiator fan can be single or dual speed depending on the market. Dual speed fans have two operating positions, high and low speed.
If the car is equipped with A/C, the radiator fan is not controlled on the basis of coolant temperature alone. Several other parameters are also taken into account:
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Coolant temperature (bus from Trionic T7)
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A/C pressure (own pressure gauge)
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Car speed (bus from MIU)
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Outside temperature (bus from SID)
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A/C system status (active/inactive)
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The information is used in DICE and determines whether the radiator fan is to be started or stopped and whether it is to run at high speed or low speed.
To maintain idling speed at a constant level, DICE sends information on the estimated current consumption. This information goes via bus to the engine management systems and is sent 0.1 seconds before DICE switches the radiator fan on or off.
To understand the operation of the radiator fan, it is important to note that it can be activated differently at the same value (within certain given limits), depending on whether the value is rising or falling.
Even after the engine has been switched off the coolant could still overheat and for this reason DICE can start the radiator fan up to 20 minutes after the ignition switch has been turned to OFF. In such case the radiator fan can only run at low speed and for a maximum of 3.5 minutes. The coolant circulates through thermosiphon action after the ignition switch has been turned to OFF.
For certain markets, cars are equipped with a radiator fan that can run at only one speed. It is controlled by DICE (628) via a relay (155). If any of the conditions is fulfilled, DICE operates the relay (155) via pin 35 and the fan motor is supplied with current.
The control module uses the following input signals for switching the radiator fan on and off.
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Coolant temperature (bus from Trionic T7)
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A/C pressure (own pressure gauge)
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Car speed (bus from MIU)
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Outside temperature (bus from SID)
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A/C system status (active/inactive)
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The fan is activated when coolant temperature matches or exceeds the preset values.
If the A/C system is active, the radiator fan can be activated in any of the following cases:
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the outside temperature exceeds 22°C (72°F)
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vehicle speed is below 38 km/h and the A/C pressure exceeds 9 bar.
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Warning
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Do not touch the fan before unplugging its connectors.
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Operation, 2-speed radiator fan with A/C
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The radiator fan may, depending on coolant temperature, A/C pressure, car speed and outside temperature, be run at two speeds:
The radiator fan is controlled by DICE via two relays, (155) and (81).
Irrespective of the position of the ignition switch, current is supplied to the low-speed relay (155) via fuse 3 and to the high-speed relay (81) via fuse 1.
Low speed
DICE uses the values which fulfil the conditions for low-speed running to start the radiator fan at low speed. The relay (155) is then grounded via pin 35 of the control unit. Current is supplied to the radiator fan which starts and runs at low speed because the current is reduced by a series resistor (367).
High speed
DICE uses the values which fulfil the conditions for running the radiator fan at high speed. The relay (81) is then grounded via pin 53 of the control unit. As a result, the series resistor (367) is bypassed and the fan is supplied with unreduced current.
The radiator fan now runs at high speed.
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Warning
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Do not touch the radiator fan before unplugging its connectors.
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Operation with ignition ON
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When the ignition switch is in the ON position, DICE uses the following information:
Without A/C
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Coolant temperature (bus from Trionic T7)
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With A/C
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Coolant temperature (bus from Trionic T7)
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A/C pressure (own pressure gauge)
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Outside temperature (bus from SID)
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A/C system status (active/inactive)
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For further information on the A/C system and its control, see
Climate system
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When the A/C clutch operates, the radiator fan is activated as follows:
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Coolant temperature
Low speed is activated when coolant temperature reaches 100°C.
Low speed is turned off when the temperature drops to 96°C.
High speed is activated when coolant temperature reaches 113°C.
High speed is turned off when the temperature drops to 109°C.
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Outside temperature
Low speed is activated when the temperature exceeds 22°C and turned off when the temperature drops below 20°C.
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Car speed / A/C pressure
Low speed is activated when car speed is below 38 km/h at the same time as A/C pressure is between 9 and 18 bar. Low speed is turned off when car speed exceeds 40 km/h or A/C pressure drops below 7 bar.
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A/C pressure
High speed is activated when A/C pressure exceeds 18 bar and turned off when A/C pressure drops below 14 bar.
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Operation with ignition OFF
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There is a risk of the coolant overheating even when the ignition is OFF. To prevent this, DICE can activate the radiator fan on the basis of information from the engine coolant temperature sensor. Coolant temperature information signals occur 30 and 60 seconds after the ignition has been turned OFF.
Using this information together with radiator fan status at ignition OFF, DICE can activate the fan (low speed if it is a 2-speed fan). The radiator fan can be activated up to 20 minutes after ignition OFF and can run for up to 3.5 minutes.
Radiator fan does not run when ignition turned from ON to OFF
30 seconds after ignition OFF:
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The radiator fan starts and runs for 3 minutes if the coolant temperature is 107°C or above. The fan stops after 3 minutes.
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The radiator fan starts and runs for 30 seconds if the coolant temperature is between 103°C and 107°C.
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60 seconds after ignition OFF:
Only applicable if the coolant temperature was between 103° and 107°C 30 seconds after ignition OFF.
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The radiator fan continues to run for 3 minutes if the coolant temperature is 107°C or above.
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The radiator fan stops if the coolant temperature is below 107°C.
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Radiator fan runs at low speed when ignition turned from ON to OFF
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The radiator fan continues to run for 30 seconds if the coolant temperature is 103°C or above.
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The radiator fan stops if the coolant temperature is below 103°C.
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30 seconds after ignition OFF:
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If the radiator fan did not stop when the ignition was turned OFF, it will continue to run for 3 minutes if the coolant temperature is 107°C or above. After 3 minutes the fan will stop. If the coolant temperature is below 107°C the fan will stop.
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If the radiator fan stopped when the ignition was turned OFF, it will start and run for 3 minutes if the coolant temperature is 107°C or above. After 3 minutes the fan will stop. If the coolant temperature is between 103°C and 107°C, the fan will start and run for 30 seconds. If the coolant temperature is below 103°C the fan will stop.
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60 seconds after ignition OFF:
Only applicable if the coolant temperature was between 103°C and 107°C 30 seconds after ignition OFF.
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The radiator fan continues to run for 3 minutes if the coolant temperature is 107°C or above.
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The radiator fan stops if the coolant temperature is below 107°C.
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Radiator fan runs at high speed when ignition turned from ON to OFF
Immediately after ignition OFF the fan starts and runs at low speed for 2 seconds. At the end of this time the same logic applies as when the radiator fan runs at low speed when the ignition is turned from ON to OFF.
