PRE-RELEASE
Detailed description, radiator fans
| Detailed description, radiator fans |
55A has 9 blades. On 65A and 75A, the left-hand fan has 9 blades and the right-hand one 11.
The radiator fans can be operated in four different steps depending on engine temperature and A/C pressure.
Stage 1
| Both fans running slowly | Fan 1 | Fan 2 |
| 55A | 45% of max speed | 60% of max speed |
| 65A | 50% of max speed | 55% of max speed |
| 75A | 43% of max speed | 45% of max speed |
Stage 2
| Both fans operate at medium speed | Fan 1 | Fan 2 |
| 55A | 75% of max speed | 75% of max speed |
| 65A | 72% of max speed | 68% of max speed |
| 75A | 70% of max speed | 70% of max speed |
Stage 3
| One fan operates at max speed and one at medium speed. | Fan 1 | Fan 2 |
| 55A | 75% of max speed | 100% of max speed |
| 65A | 72% of max speed | 100% of max speed |
| 75A | 70% of max speed | 100% of max speed |
Stage 4
| Both fans running at max speed | Fan 1 | Fan 2 |
| 55A | 100 % | 100 % |
| 65A | 100 % | 100 % |
| 75A | 100 % | 100 % |
The radiator fans have their own relay unit and are controlled by ECM via UEC. The fans are controlled by ECM using the following signals:
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Coolant temperature
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A/C pressure
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Fluid temperature from automatic transmission
Relay unit, radiator fans (706), supplied with +30 voltage from the radiator fan fuse holder to pins 3 and 6 and grounded to G2 from pins 5 and 2. There are 3 cables coming from ECM via the underhood electrical centre to the relay unit. These cables are connected to pins 1, 4 and 7 on the relay unit. The four different speed stages of the radiator fans are obtained depending on the connections being grounded and the combinations in which the grounding of the connections is done. 
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| The radiator fans start in the following cases: |
Temperature logic
Step 1 on the radiator fans commences when the coolant temperature reaches 98°C (208 F) and stops when the temperature has dropped to 96°C (204 F).
Step 2 on the radiator fans commences when the coolant temperature reaches 101°C (213 F) and step 1 recommences at 99°C (210 F).
Step 3 on the radiator fans commences when the coolant temperature reaches 103°C (217 F) and step 2 recommences at 101°C (213 F).
Step 4 on the radiator fans commences when the coolant temperature reaches 105°C (221 F) and step 3 recommences at 103°C (217 F).
A/C pressure logic
The following values apply to absolute pressure:Stage 1 on the radiator fans starts at an A/C pressure over 1300 kPa and ceases at a pressure below 1000 kPa.
Step 2 on the radiator fans starts at an A/C pressure over 1800 kPa and returns to step 1 at a pressure of 1500 kPa.
Step 3 on the radiator fans starts at an A/C pressure over 2200 kPa and returns to step 2 at a pressure of 1800 kPa.
Step 4 on the radiator fans starts at an A/C pressure over 2500 kPa and returns to step 3 at a pressure of 2200 kPa.
If the temperature signal is missing, the radiator fans will run constantly at full speed, i.e. stage 4.
| Operation with ignition ON |
With the ignition switch turned to ON, ECM will use the following information on the bus:
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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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This information is used by ECM to control starting and stopping the radiator fans.
A/C is disengaged if the coolant temperature exceeds 120°C (247 F) and re-engages at 118°C (244 F).
A/C is disengaged if the A/C pressure exceeds 2800 kPa and is reengaged at 2300 kPa.
Idle speed compensation
In order to maintain a constant idling speed when the radiator fans are turned on or off, there is a 3 second delay before the fans are engaged. During this time, the engine control module will start to compensate for the increased load so that the idling speed will not drop when the radiator fans start.| Function for ignition OFF/LOCK |
ECM controls the fans depending on the engine temperature when the ignition is in OFF/LOCK. If the temperature is below 100°C (212 F) the radiator fans will remain off but if the temperature exceeds 105°C (221 F), the fans will go on at 103°C (217 F) and stay on for 120 seconds.
Note that only step 1 is activated if the ignition is OFF/LOCK.
