Cooling System: Description and Operation
Regardless of the position of the ignition switch, current is supplied to relay 155 via fuse 4 and to relay 81 via max fuse 2.The radiator fan is controlled by the EDU control module.
The engine coolant temperature is measured by the EDU control module, which controls relay 155.
Single-Speed Radiator Fan
When the temperature reaches about 100 °C (212 °F), relay 155 operates and radiator fan 37 starts. When the temperature drops to about 96 °C (205 °F), the fan stops.
2-Speed Radiator Fan 366
In some markets, cars equipped with A/C have a 2-speed radiator fan for more efficient cooling.
The first stage (speed 1) operates as described above. The radiator fan starts at low speed
When the coolant temperature reaches 111 °C (232 °F), relay 81 is grounded via the EDU control module. The radiator fan runs at full speed. When the coolant temperature drops to 107 °C (225 °F), fan speed returns to speed 1 (low speed).
Cars With A/C
When the ignition is switched on, relay 433 operates and connects the A/C system's 3-stage pressure switch 166 in parallel with the EDU control module.
When the intermediate pressure switch closes, relay 155 is grounded via relay 433. Relay 155 operates and the radiator fan starts irrespective of the coolant temperature. When the pressure in the A/C system drops and the intermediate pressure switch opens, the fan will stop unless the coolant temperature is such as to cause the EDU control model to ground relay 155.
Radiator Fan Switch-off Relay 433
To prevent the battery from being drained when the radiator fan continues to run after the engine has been switched off, relay 433 breaks the circuit to the 3-stage pressure switch as soon as the ignition is switched off.
However, the EDU control module can cause relay 155 to operate so that the fan will continue to run at speed 1 (low speed). The time is then limited to 3.5 minutes.
Extra Pressure Switch 419
In certain markets, the A/C system is equipped with an extra pressure switch which controls relay 81. If the refrigerant pressure exceeds 22 bar, the contact will close. This causes relay 81 to operate and engages speed 2 on radiator fan 37.