PRE-RELEASE
Detailed description, radiator fans
| Detailed description, radiator fans |
For 55A, both fans have 9 blades. For 65A and 75A, the left fan has 9 blades and the right fan has 11 blades.
The radiator fans can be run at four different speeds depending on engine temperature and A/C pressure.
Speed 1
| Both fans run at slow speed | Fan 1 | Fan 2 |
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55A
|
45% of max. speed
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60% of max. speed
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65A
|
50% of max. speed
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55% of max. speed
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|
75A
|
43% of max. speed
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45% of max. speed
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Speed 2
| Both fans run at medium speed | Fan 1 | Fan 2 |
|
55A
|
75% of max. speed
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75% of max. speed
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65A
|
72% of max. speed
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68% of max. speed
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|
75A
|
70% of max. speed
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70% of max. speed
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Speed 3
| One fan runs at max. speed and the other runs at medium speed | Fan 1 | Fan 2 |
|
55A
|
75% of max. speed
|
100% of max. speed
|
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65A
|
72% of max. speed
|
100% of max. speed
|
|
75A
|
70% of max. speed
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100% of max. speed
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Speed 4
| Both fans run at max. speed | Fan 1 | Fan 2 |
|
55A
|
100 %
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100 %
|
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65A
|
100 %
|
100 %
|
|
75A
|
100 %
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100 %
|
The radiator fans have their own relay and are regulated by ECM via UEC. The fans are regulated by ECM via the following input signals:
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Coolant temperature
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| • |
A/C pressure
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| • |
Automatic transmission fluid temperature
Radiator fan relay (706) is supplied +30 from the radiator fan fuse holder to pins 3 and 6 and is grounded in G2 from pins 5 and 2. 3 cables run from ECM to the relay unit via the underhood electrical centre. These cables are connected to pins 1, 4 and 7 on the relay unit. Depending on which connetions are grounded and in which combination the connections are grounded, there are four different radiator fan speeds. 
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| The radiator fans start in the following cases: |
Temperature logic
Radiator fan speed 1 is initiated when coolant temperature reaches 98°C (208 F) and is deactivated when temperature falls to 96°C (204 F).
Radiator fan speed 2 is initiated when coolant temperature reaches 101°C (213 F) and returns to speed 1 at 99°C (210 F).
Radiator fan speed 3 is initiated when coolant temperature reaches 103° C (217 F) and returns to speed 2 at 101° C (213 F).
Radiator fan speed 4 is initiated when coolant temperature reaches 105° C (221 F) and returns to speed 3 at 103° C (217 F).
A/C pressure logic
The following values apply at absolute pressure:Radiator fan speed 1 is initiated at A/C pressure over 1300 kPa. The radiator fans are deactivated when pressure is below 1000 kPa.
Radiator fan speed 2 is initiated when A/C pressure exceeds 1800 kPa. The radiator fans return to speed 1 at a pressure of 1500 kPa.
Radiator fan speed 3 is initiated when A/C pressure exceeds 2200 kPa. The radiator fans return to speed 2 at a pressure of 1800 kPa.
Radiator fan speed 4 is initiated when A/C pressure exceeds 2500 kPa. The radiator fans return to speed 3 at a pressure of 2200 kPa.
If there is no temperature signal, the radiator fans will always run at full speed (speed 4).
| Operation with ignition ON |
When the ignition switch is in the ON position, ECM uses the following information on the bus:
| • |
Coolant temperature (bus from ECM)
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| • |
A/C pressure
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| • |
A/C system status (active/inactive)
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The information is used by ECM to determine whether the radiator fans are to be started or stopped.
A/C is deactivated if coolant temp. exceeds 120°C (247 F) and is reactivated at 118°C (244 F).
A/C is deactivated if A/C pressure exceeds 2800 kPa and is reactivated at 2300 kPa.
Idle compensation
To keep idling speed constant when the radiator fans are activated or deactivated, there is a 3-second delay to radiator fan activation. During this time, the engine management system starts to compensate for the increased load so that idling speed does not fall when the radiator fans start.| Operation with ignition OFF/LOCK |
ECM regulates the fans when the ignition is set to OFF/LOCK based on engine temperature. If temperature is below 100°C (212 F), the radiator fans remain off. If temperature exceeds 105°C (221 F), the fans start at 103°C (217 F) and run for 120 seconds.
Note that only speed 1 is activated when the ignition is set to OFF/LOCK.
