Electric Cooling Fans: Operation
Radiator cooling fans operate at two speeds (Low and High), and are simultaneously activated. Dual cooling fan system improves engine cooling and A/C performance in hot weather and severe driving conditions, while reducing fan noise and power consumption.
Radiator cooling fans will operate based on inputs to Powertrain Control Module (PCM). When radiator cooling fan operation is determined necessary, PCM provides ground to fan relay control circuit. Inputs provided to PCM that influence radiator cooling fan operation are: Engine Coolant Temperature (ECT) sensor, Intake Air Temperature (IAT) sensor, Output Speed Sensor (OSS), Transmission Oil Temperature (TOT) sensor, and A/C pressure transducer. The A/C pressure transducer on A/C compressor discharge line sends a signal to PCM that will activate both fans if required. In addition to this control, radiator fans are turned on through fan relays based on coolant temperature, intake air temperature, transmission oil temperature and output speed sensors. See Fig 1 and Fig 2 . Radiator cooling fans will not operate during engine cranking, regardless of coolant temperature.
On models with 2.7L base engine, both fans operate at 2 different speeds, low and high, depending on engine coolant temperature and A/C system high-side pressure. PCM controls radiator fan speed by grounding coil side of either HI/LO fan relay or HI fan relay. Ignition switch supplies voltage to coil sides of relay. When PCM grounds coil side of relay, contacts close and battery power is supplied to cooling fans. See WIRING DIAGRAMS .
On models without 2.7L base engine, both fans operate at 2 different speeds, low and high, depending on engine coolant temperature and A/C system high-side pressure. PCM controls radiator fan speed by grounding coil side of either HI/LO fan relay or HI fan relay. Low speed radiator fan operation is achieved by running both fan motors in a series circuit. High speed radiator fan operation is achieved by running both fan motors in a parallel circuit. See WIRING DIAGRAMS .