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The engine cooling fan system consists of 2 electric cooling fans. The engine control module (ECM) commands via a pulse width modulated (PWM) signal the cooling fan control module ON in either high speed, medium speed, or low speed, depending on cooling requirements. In low speed, the fans are turned ON at a reduced speed. In medium speed, the fans are turned ON at a higher reduced speed. In high speed, the fans are turned ON at full speed. The cooling fan control module is supplied with B+ and ground. It contains 2 drivers that control the 2 cooling fans, depending on cooling requirements that were sent by the PWM signal from the ECM.
The engine cooling fan system consists of 2 electric cooling fans and 3 fan relays. The cooling fan relays are arranged in a series/parallel configuration. This allows the engine control module (ECM) to operate both fans together at low or high speeds using 2 fan control circuits. When commanded on, the cooling fans receive battery positive voltage from the switch side of the cooling fan relays, which is supplied through a fuse by the underbonnet fuse block. The cooling fans are supplied with ground.
The ECM applies ground to the coil side of the cooling fan left high speed relay. This energises the coil and applies voltage directly to the left cooling fan through the switch side of the relay. The left cooling fan is connected in series to the right cooling fan through the de-energised series/parallel cooling fan speed control relay. The result is a series circuit that operates both fans at low speed.
The ECM applies a ground to the coil side of the cooling fan left high speed relay, the series/parallel cooling fan speed control relay, and the cooling fan right high speed relay. When energised, the right high speed fan relay applies voltage directly to the right cooling fan through the switch side of the relay. Simultaneously, the left high speed relay and the series/parallel speed control relay provide ignition voltage and a direct path to ground for the left cooling fan. During high speed fan operation, both engine cooling fans have their own ground path. The result is a parallel circuit with both fans operating at high speed.
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