Detailed Description, Radiator Fans
Detailed description, radiator fansRadiator fan logic
The car is equipped with two radiator fans located behind the radiator. The fans have 11 blades with diameter 320 mm and can be operated in four different stages depending on engine temperature and A/C pressure.
The radiator fans have their own relay box and communication between ECM and the radiator fan relay box is achieved through a cable via UEC.
The fans are controlled by ECM through the following input signals:
^ Coolant temperature
^ A/C pressure
^ Fluid temperature from automatic transmission
Radiator fan relay box (706) is supplied with +30 from UEC to pins 3 and 6, and is grounded to G30A from pins 5 and 2.
From ECM come 3 cables via the underhood electrical centre to the relay box. These cables are connected to pins 1, 4 and 7 on the relay box. Depending on the connection being grounded and the combination in which they are grounded, four different speed stages can be obtained for the radiator fans.
The radiator fans start in the following cases:
1. Temperature logic:
Stage 1 on the radiator fans starts when the coolant temperature has reached 100°C and stops when the temperature has dropped to 96°C.
Stage 2 on the radiator fans starts when the coolant temperature has reached 108°C and returns to stage 1 at 104°C.
Stage 3 on the radiator fans starts when the coolant temperature has reached 114°C and returns to stage 2 at 110°C.
Stage 4 on the radiator fans starts when the coolant temperature has reached 120°C and returns to stage 3 at 116°C.
2. A/C pressure logic
Stage 1 on the radiator fans starts at an A/C pressure over 1100 kPa and stops at a pressure below 800 kPa.
Stage 2 on the radiator fans starts at an A/C pressure over 1700 kPa and returns to stage 1 at a pressure of 1400 kPa.
Stage 3 on the radiator fans starts at an A/C pressure over 2000 kPa and returns to stage 2 at a pressure of 1800 kPa.
Stage 4 on the radiator fans starts at an A/C pressure over 2300 kPa and returns to stage 3 at a pressure of 2100 kPa.
If the automatic transmission fluid temperature rises to 140°C, the radiator fans will start at stage 4 irrespective of the temperature of the engine and the pressure in the A/C system. Once the transmission temperature has dropped to 130°C, the radiator fans will return to normal logic.
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:
^ Coolant temperature (bus from ECM)
^ A/C pressure
^ A/C system status (active/inactive)
^ Transmission temperature
This information is used by ECM to control starting and stopping the radiator fans.
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.
Current consumption
The approximate current consumption of the radiator fans during at the various stages is as follows:
Maximum current must not exceed 40A in "Stage 4".
Operation with ignition OFF
ECM controls the fans when the ignition is "OFF" depending on the engine temperature. If the temperature is below 100 degrees, they will not be turned on but if the temperature exceeds:
100°C, the radiator fans will keep running for 30 seconds
105°C, the radiator fans will keep running for 90 seconds
110°C, the radiator fans will keep running for 150 seconds
115°C, the radiator fans will keep running for 210 seconds
120°C, the radiator fans will keep running for 270 seconds
The radiator fans then run in "Stage 1" and the temperature will be measured again every 30 seconds.
Note that only "Stage 1" is active with the ignition OFF.