Aurora V8-4.0L VIN C (1996)
Radiator Cooling Fan Motor: Description and Operation
Cooling System
The electric cooling fans are used to cool engine coolant flowing through the radiator. They are also used to cool the refrigerant flowing through the
A/C condenser.
The electric cooling fans are controlled by the PCM. The PCM controls the ground path for the three cooling fan relays. The relays are used to control
the high current flow to power the cooling fan motors. Both fans operate together. When minimum cooling is required, the PCM energizes the low
speed cooling fan relay No. 1, and both fans operate at low speed since the fans are connected in series thorough the series/parallel cooling fan relay
No. 2. The series/parallel coolant fan relay is a dual position switch and while de-energized, supplies a ground path for the low speed fan circuit.
When maximum cooling is required, the PCM energizes all three cooling fan relays. The left hand coolant fan is still power through the low speed
cooling fan relay No. 1, but is now grounded through the series/parallel cooling fan relay No. 2 and operates at high speed. The right hand coolant fan
is powered directly through the high speed cooling fan relay No. 3 and also operates at high speed.
The low speed cooling fans are controlled by the PCM based on inputs from the A/C system, Engine Coolant Temperature (ECT) sensor and Vehicle
Speed Sensor (VSS). The PCM will command low speed fans to turn On when ECT sensor is above 223° F. The PCM will turn the fans Off when the
temperature drops about 5° F. The minimum On time for low speed fans is 50 seconds.
The PCM will command high speed fans to turn On at idle when a certain DTC is set, the ECT is above 230° F or the A/C head pressure is above 248
psi. If the high speed fans were turned On by the ECT, the PCM will switch the fans back to low speed when the temperature drops about 5° F.
Minimum On time for high speed fans is 30 seconds.
