Circuit/System Description

WARNING: This page is about a different car, the 2009 Saturn Vue. However, it is still accessible from the selected car via links, so may be relevant.

The engine control module (ECM) commands the fans ON in high speed or low speed. In low speed, the fans are configured in series. In high speed, the fans are configured in parallel.

In low speed operation, the ECM applies ground to the coil side of fan relay. Voltage is applied directly to the left cooling fan through the switch side of low speed fan relay, which is FAN AUX relay 3. The right fan is connected in series to the left fan through the de-energized series/parallel relay, which is FAN CTRL relay, so that both fans operate at low speed.

In high speed operation, the ECM applies a ground to the coil side of low speed relay, series/parallel relay, and high speed fan relay, which is FAN MAIN relay. Voltage is applied directly to the right cooling fan through the switch side of fan main relay. The left cooling fan obtains voltage through low speed relay and ground through series/parallel relay.

When the ECM is commanding a fan relay ON, the voltage of the control circuit should be low, near 0 volts. When the ECM is commanding a fan relay OFF, the voltage of the control circuit should be high, near battery voltage.