Circuit/System Description
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 (S/P) configuration. This allows the engine control module (ECM) to operate both fans together at low or high speeds using 2 fan control circuits. The cooling fans receive positive voltage from the cooling fan relays, which receive battery positive voltage from the underhood fuse block. The cooling fans are supplied a ground at G100 and G101.
The hybrid engine cooling fan system consists of two electrical cooling fans, two resistors, three engine control module (ECM) fan control circuits, and five fan relays. The relays are arranged in a series/parallel configuration that allows the ECM to operate the fans at low, medium, or high speed depending on cooling requirements. The ECM controls the five relays by grounding the relay control circuits.
To operate the fans, the ECM activates the applicable relay by grounding the control circuit with a solid state device called a driver. The driver is equipped with a feedback circuit. The ECM can determine if the control circuit is open, shorted to ground, or shorted to a voltage by monitoring the feedback voltage. 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-termperature condition. This condition occurs when the coolant temperature is above a calibrated value for a calibrated length of time. The ECM will disable half of the cylinders by turning OFF the fuel injectors. By disabling half of cylinders, the ECM is able to reduce the temperature of the coolant.
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 (S/P) configuration. This allows the engine control module (ECM) to operate both fans together at low or high speeds using 2 fan control circuits. The cooling fans receive positive voltage from the cooling fan relays, which receive battery positive voltage from the underhood fuse block. The cooling fans are supplied a ground at G100 and G101.
The hybrid engine cooling fan system consists of two electrical cooling fans, two resistors, three engine control module (ECM) fan output control drivers, and five fan relays. The relays are arranged in a series/parallel configuration that allows the ECM to operate the fans at low, medium, or high speed depending on engine cooling requirements. The ECM controls the five relays by grounding the relay control circuits.
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 (S/P) configuration. This allows the engine control module (ECM) to operate both fans together at low or high speeds using 2 fan control circuits. The cooling fans receive positive voltage from the cooling fan relays, which receive battery positive voltage from the underhood fuse block. The cooling fans are supplied a ground at G100 and G101.
The hybrid engine cooling fan system consists of two electrical cooling fans, two resistors, three engine control module (ECM) fan output control drivers, and five fan relays. The relays are arranged in a series/parallel configuration that allows the ECM to operate the fans at low, medium, or high speed depending on engine cooling requirements. The ECM controls the five relays by grounding the relay control circuits.
The optional coolant heater is a heating element that mounts in the engine block in place of an existing anti-freeze plug. The coolant heater operates using an external 110 volt AC power source and is designed to warm the coolant in the engine block for improved starting in very cold weather. The coolant heater also helps reduce fuel consumption when a cold engine is warming up. The detachable AC power cord contains an internal thermal switch that opens, to prevent operation when the ambient temperature is warmer than -10°C (14°F), and closes at -18°C (0°F) to allow operation. The power cord is also equipped with a weather shield to protect the plug when not in use.
System Overview
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 (S/P) configuration. This allows the engine control module (ECM) to operate both fans together at low or high speeds using 2 fan control circuits. The cooling fans receive positive voltage from the cooling fan relays, which receive battery positive voltage from the underhood fuse block. The cooling fans are supplied a ground at G100 and G101.
Low Speed Operation
The ECM applies ground to the coil side of the cooling fan low speed relay. This energizes the coil and applies voltage directly to the left cooling fan through the switch side of the low speed relay. The left cooling fan is connected in series to the right cooling fan through the de-energized series/parallel (S/P) cooling fan speed control relay. The result is a series circuit that operates both fans at low speed.
High Speed Operation
The ECM applies a ground to the coil side of the cooling fan low speed relay, the S/P cooling fan speed control relay, and the cooling fan high speed relay. When energized, the high speed fan relay applies voltage directly to the right cooling fan through the switch side of the relay. Simultaneously, the low speed fan relay and the S/P 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.
The hybrid engine cooling fan system consists of two electrical cooling fans, two resistors, three engine control module (ECM) fan output control drivers, and five fan relays. The relays are arranged in a series/parallel configuration that allows the ECM to operate the fans at low, medium, or high speed depending on engine cooling requirements. The ECM controls the five relays by grounding the relay control circuits.
The ECM applies a ground to the fan 1 control circuit for the low fan relay. This energizes the low fan relay coil, closes the relay contacts, and supplies battery positive voltage from the fan 1 fuse through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the de-energized fan control relay, through the right cooling fan in-line resistor, and right cooling fan. The result is a series circuit with both fans running at a reduced speed.
Medium Speed Operation
The ECM applies a ground to the fan 2 control circuit, which energizes a bank of three relays consisting of the FAN Mid 1 relay, the fan control relay, and the FAN Mid 2 relay. When these three relays are energized the Mid 1 relay supplies battery voltage to the left cooling fan through the left cooling fan resistor. A direct ground path is provided for the left fan through the energized fan control relay. At the same time the Mid 2 relay is energized which applies battery voltage to the right cooling fan through the right cooling fan resistor. The result is a parallel circuit where each fan has voltage applied through a separate resistor, causing each fan to operate at a medium speed.
The ECM applies a ground to the fan 1, fan 2, and fan 3 relay control circuits simultaneously, which activates all five relays. This allows battery voltage to be applied directly to the right cooling fan from the Fan High relay, and battery voltage to be applied directly to the left fan from the Fan Low relay. The left fan is supplied a direct path to ground through the energized fan control relay. This arrangement provides each fan with direct battery voltage and its own ground path. The result is a parallel circuit with both fans running at full speed. 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.