Circuit/System Description
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 the low speed fan relay, which is the cool/fan 1 relay 28. Voltage is applied directly to the left cooling fan through the switch side of the low speed fan relay. The right fan is connected in series to the left fan through the de-energized series/parallel relay, which is cool/fan SER/PAR relay 29, so that both fans operate at low speed.
In high speed operation, the ECM applies a ground to the coil side of the low speed fan relay, the series/parallel relay, and the high speed fan relay, which is cool/fan 2 relay 30. Voltage is applied directly to the right cooling fan through the switch side of the high speed fan relay. The left cooling fan obtains voltage through the low speed relay and ground through the 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.
The engine control module (ECM) uses the engine coolant temperature (ECT) sensor to monitor the engine for an over-temperature condition. This condition occurs when the coolant temperature is above a calibrated value. The ECM will alternately disable 2 groups of cylinders by turning OFF the fuel injectors. By switching between the 2 groups of cylinders, the ECM is able to reduce the temperature of the coolant.
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 the low speed fan relay, which is the coo/fan relay 28. Voltage is applied directly to the left cooling fan through the switch side of the low speed relay. The right fan is connected in series to the left fan through the de-energized fan/control relay, which is cool/fan SER/PAR relay 29, so that both fans operate at low speed.
In high speed operation, the ECM applies a ground to the coil side of the low speed fan relay, the series/parallel relay, and the high speed fan relay, which is the cool/fan 2 relay 30. Voltage is applied directly to the right cooling fan through the switch side of the high speed fan relay. The left cooling fan obtains voltage through the low speed fan relay and ground through the 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.
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 the low fan speed relay, which is the cool/fan 1 relay 28. Voltage is applied directly to the left cooling fan through the switch side of the low speed fan relay. The right fan is connected in series to the left fan through the de-energized series/parallel relay, which is cool/fan SER/PAR relay, so that both fans operate at low speed.
In high speed operation, the ECM applies a ground to the coil side of the low speed fan relay, the series/parallel relay, and the high speed fan relay, which is the cool/fan relay 30. Voltage is applied directly to the right cooling fan through the switch side of the high speed fan relay. The left cooling fan obtains voltage through the low speed fan relay and ground through the 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.
The optional coolant heater operates using 110-volt AC external power and is designed to warm the coolant in the engine block area for improved starting in very cold weather. There is an internal thermal switch in the power cord that prevents operation above -18°C (0°F). The coolant heater helps reduce fuel consumption when a cold engine is warming up. The unit is equipped with a detachable AC power cord. A weather shield on the cord is provided to protect the plug when not in use.