Introduction

Typical Example (100-8105 Shown)

The fan clutch is a mechanically actuated, oil pressure activated, oil cooled and lubricated, multi plate clutch designed to provide variable fan speed. Engine (sump) lubricating oil is piped to the fan clutch to provide a supply of filtered and cooled oil. Internal ports and orifices distribute lubricating/cooling oil, and oil control pressure which controls fan speed by modulating the engagement and disengagement of the fan clutch.

The fan clutch operates at 100 to 300 rpm (minimum speed) when there is not any oil pressure applied to the fan clutch. The fan clutch operates at 800 to 1150 rpm (depending on application) when there is a constant oil pressure applied to the fan clutch.

The amount of cooling required by the fan clutch is based on the following controlled inputs:

* Coolant temperature

* Brake oil temperature

* Aftercooler temperature

* Air conditioner pressure (if equipped)

The solenoid adjusts control oil pressure to the fan clutch based on inputs from the coolant temperature sensor and brake oil temperature sensors. The aftercooler temperature switch and air conditioner pressure switch override the signal to the solenoid valve when the activation temperature or pressure has been reached. When conditions warrant (high exhaust temperature, the air conditioner is in use, or heavy retarding conditions are present) the override capability provides maximum fan speed.

Modulated control of the fan clutch by the solenoid valve cause the fan speed to be increased or decreased smoothly without shock loads. Oil cooled plates permit clutch slippage which results in variable fan speed.

Components

Typical Example (100-8105 Shown)
(1) Lock washer (only on 100-8105 and 129-9494). (2) Fan pulley adapter. (3) Bearing retainer (front). (4) Clutch plates. (5) Bolt (only on 100-8105 and 129-9494). (6) Snap ring (external). (7) Oil seal (rear). (8) Bearing retainer (rear) (only on 100-8105 and 129-9494). (9) Main bearing (rear). (10) Snap ring (internal). (11) Snap ring (internal). (12) Main bearing (front). (13) Oil seal (front). (14) Seal ring. (15) Hub. (16) Wear sleeve. (17) Shaft and bracket assembly. (18) Retainer. (19) Snap ring (external). (20) Snap ring (external). (21) Pitot tube assemblies. (22) Sleeve bearing. (23) Wear sleeve (front). (24) Retainer. (25) Fan mounting hub. (26) End cap. (27) Seal ring. (28) Seal ring. (29) Clutch body assembly. (30) Spring washer. (31) Seal ring. (32) Annular shim. (33) Clutch piston. (34) Seal ring. (35) Clutch plate assembly. (36) Sleeve bearing.

Hydraulically Driven Components

The control pressure from the solenoid pushes the piston which in turn pushes the clutch plate assemblies against the clutch plates which are splined to the hub.

Pulley Driven Components

The clutch is driven by the fan belt through a pulley which is bolted to the fan pulley adapter (2) and bearing retainer(s) which are bolted together forming the pulley cavity. The pulley cavity is sealed at the shaft and bracket assembly (17) and fan mounting hub (25) by rotating seals (7) and (13) and is supported by ball bearings. The slotted cup section of the front bearing retainer drives the externally tanged steel clutch plates (4).

Stationary Components

The shaft and bracket assembly (17) is bolted to the engine and supports the fan clutch components. Pitot tube assemblies (21) are fastened to the shaft. The pitot tube assemblies (21) returns oil to the engine.

Control Systems

Analog Controlled

The analog (PWM sensor) controlled system provides the capability for the fan clutch to operate at modulated speeds. Each temperature sensor acts independently to provide a pulse width modulated signal to the solenoid valve (variable signal) which varies the fan speed in addition to the temperature sensor(s), override switches which de-energize the solenoid valve allowing maximum oil pressure to be sent to the fan clutch.

The control system has two configurations for maintaining proper cooling depending on engine size. One configuration for the 6I4427 Fan Clutch consists of the following:

* Fan clutch solenoid valve

* Coolant temperature sensor

* Aftercooler temperature switch

* Air conditioner pressure switch

* Brake oil temperature switch

The second configuration is used on the 100-8105 Fan Clutch. This control system is fundamentally the same as the control system used on the 6I4427 Fan Clutch.

The only differences are that a brake oil sensor is used in place of the brake oil switch, and a relay is added for the switch overrides. The configuration for 100-8105 Fan Clutch consists of the following:

* Fan clutch solenoid valve

* Coolant temperature sensor

* Aftercooler temperature switch

* Air conditioner pressure switch

* Brake oil temperature sensor

* Relay

The fan clutch solenoid valve supplies a control pressure to the fan clutch. This solenoid is normally open (energized) bypassing control oil back to the engine. The solenoid valve modulates when the minimum temperature values for the sensor(s) have been reached. This sends control oil to the fan clutch. The solenoid valve closes (de-energized) when the air conditioner, aftercooler switch or brake oil switch (if equipped) have been activated or the sensor temperature(s) have reached a value that requires maximum cooling.

The coolant temperature sensor provides a pulse width modulated signal (PWM). The PWM signal. The PWM signal provides a direct input to the solenoid valve. The PWM signal is at a maximum when the cooling requirements for the engine are at a minimum. The maximum PWM signal holds the solenoid valve in the bypass mode and no oil pressure is applied to the fan clutch. In this mode the fan is at a minimum speed and rotating only due to viscous drag in the fan clutch, 100 to 300 rpm depending on oil viscosity. The coolant temperature sensor provides a variable signal input to the solenoid at temperatures between 88°C (190°F) and 93°C (200°F) allowing a variable fan speed. As the temperature nears 93°C (200°F), the signal approaches its minimum width and the fan speed nears its maximum. When the coolant temperature exceeds 93°C (200°F), the control pressure to the clutch becomes constant and full fan speed is attained.

The brake oil temperature sensor (if equipped) operates exactly like the coolant temperature sensor except the sensor begins modulating the solenoid at 102°C (215°F) and maximum fan speed is achieved when the brake oil temperature reaches 107°C (225°F).

When the brake oil temperature switch (if equipped) exceeds 107°C (225°F), the normally open switch closes and completes a grounded circuit with the coolant temperature sensor. When the coolant temperature sensor is grounded it disconnects power from the oil supply solenoid regardless of the coolant temperature. This allows maximum control oil pressure to be provided to the fan clutch and maximum fan speed is attained.

The aftercooler switch monitors the aftercooler coolant temperature. This input overrides the coolant temperature sensor and the brake oil temperature sensor (if equipped). When the aftercooler coolant temperature exceeds 82°C (180°F), the normally open switch closes and completes a ground circuit with the coolant temperature sensor. When the coolant temperature sensor is grounded it disconnects power from the fan clutch solenoid regardless of the coolant temperature.

The air conditioner pressure switch monitors the pressure in the air conditioner system. Operation of the air conditioner requires additional cooling. When the condenser pressure exceeds 1585 kPa (230 psi), the normally open switch closes and completes a ground circuit with the coolant temperature sensor. When the coolant temperature sensor is grounded it disconnects power from the fan clutch solenoid regardless of the coolant temperature.

The override relay (if equipped) is used to send the ground signal from the A/C override or aftercooler override switches to the sensors.

ECM Controlled

The ECM controlled system provides the capability for the fan clutch to operate at modulated speeds. The temperature sensor provides a digital signal to the ECM. The engine speed/timing sensor and engine fan speed sensor are used to override the sensor by de-energizing the solenoid valve allowing the maximum oil pressure to the fan clutch.

The ECM controlled system has two configurations for maintaining proper cooling depending on engine size. One configuration is used on the 123-6968 and 136-7609 Fan Clutch and consists of the following:

* Fan clutch solenoid valve

* Coolant temperature sensor

* Engine speed/timing sensor

* Engine fan speed sensor

* Air conditioner interface relay

* ECM

* Aftercooler temperature sensor (if equipped)

The second configuration is used on the 129-9494 Fan Clutch. This control system is fundamentally the same as the control system used on the 123-6968 and 136-7609 Fan Clutch. The only differences are that a brake oil temperature sensor and an aftercooler temperature sensor have been added and an air/conditioner pressure switch is used in place of the air conditioner interface relay.

* Fan clutch solenoid valve

* Aftercooler temperature sensor

* Brake oil temperature sensor

* Coolant temperature sensor

* Engine speed/timing sensor

* Air conditioner pressure switch

* Engine fan speed sensor

* ECM

The fan clutch solenoid valve supplies a control pressure to the fan clutch. The solenoid is normally open (energized) bypassing control oil back to the engine. The solenoid valve modulates when the minimum coolant temperature value has been reached or the air conditioner has been activated or the fan speed sensor is not within ± 50 rpm of the desired fan speed and these conditions allow oil pressure to the fan clutch.

The coolant temperature sensor provides a signal to the ECM. The ECM varies the current to the fan clutch solenoid valve. The current to the solenoid is high when the cooling requirements for the engine are at a minimum. The maximum current holds the solenoid valve in the bypass mode and no oil pressure is applied to the fan clutch. In this mode the fan is at a minimum speed and rotating only due to viscous drag in the fan clutch, 100 to 300 rpm depending on oil viscosity. The coolant temperature sensor provides a signal input to the ECM at temperature between 88°C (190°F) and 98°C (208°F) allowing a variable fan speed. When the coolant temperature exceeds 98°C (208°F), the control pressure to the clutch becomes constant and full fan speed is attained.

The brake oil temperature sensor (if equipped) operates exactly like the coolant temperature sensor except the ECM begins modulating the solenoid at 102°C (215°F) and maximum fan speed is achieved when the brake oil temperature reaches 107°C (225°F).

The aftercooler temperature sensor (if equipped) operates exactly like the coolant temperature sensor except the ECM begins modulating the solenoid at 78°C (172°F) and maximum fan speed is achieved when the brake oil temperature reaches 88°C (190°F).

The engine speed/timing sensor provides an input to the control system. When the engine speed/timing sensor senses an overspeed condition, the ECM will set the fan speed to a maximum by sending a lower current to the solenoid valve. If no current is supplied to the solenoid valve then the fan clutch is locked up at its maximum speed.

The engine fan speed sensor is used to measure the actual fan speed. If the actual fan speed is within ± 50 rpm of the desired fan speed then the ECM will not adjust the current to the solenoid valve. If there is a problem with the fan speed sensor a fault is generated and current to the solenoid is controlled based only on coolant temperature. The ECM will no longer be able to measure the actual fan speed and adjust the current supplied to the solenoid valve in order to obtain a desired fan speed for the required cooling capacity.

The air conditioner interface relay (if equipped) sends a signal to the ECM. When the air conditioner is activated the ECM processes the interface relay signal and sends a current to the solenoid valve. This current corresponds to a fan speed of 450 rpm.

The air conditioner pressure switch (if equipped) monitors the pressure in the air conditioner system. Operation of the air conditioner requires additional cooling. When the air condenser pressure exceeds 1585 kPa (230 psi), the normally open switch closes and the ECM controlled system sends a low current to the solenoid for maximum fan speed.

The ECM varies the current level (0.4 to 1.9 Amps) to the solenoid valve in order to maintain an actual fan speed that meets the required cooling capacity. The current can be observed on an electronic service tool as "Eng Fan Bypass". By adjusting current to the solenoid the ECM is adjusting the control pressure supplied to the clutch. If there is a problem with the current supplied to the solenoid valve a fault is generated and the current is set to a minimum value. The ECM will periodically check the electrical system by changing the current level to the solenoid.

Lubrication System

Typical Example (100-8105 And 129-9494)
(1) Oil inlet port (lube oil). (2) Oil control port (control oil). (3) Oil outlet port (oil out).

Typical Example (Rear View) (6I4427, 136-7609 And 123-6968)
(1) Oil inlet port (lube oil). (2) Oil control port (control oil). (3) Oil outlet port (oil out).

Typical Example (6I4427, 136-7609 And 123-6968)

Filtered lubricating and cooling oil is supplied to the fan clutch from the engine oil pressure system. The engine oil travels through the supply line from the engine to the oil inlet port (1) on the shaft and bracket assembly of the fan clutch. The oil flows through the inlet port (1) and into the shaft. Some applications do not require an orifice in the oil inlet port (1), refer to the parts book for your application. Oil passages in the shaft distribute lubricating oil to the bearings, other internal components, and into the splined hub cavity. Centrifugal force drives the oil through holes in the clutch hub to cool the clutch plates. The grooved configuration of the clutch plate assembly allows oil to pass over the clutch plates at all times. The flow of cooling oil over the clutch plates permits clutch slip and variable fan speeds.

Centrifugal force carries the oil outward to the ID of the pulley. The rotational movement of the pulley carries the oil in the direction of the pulley rotation. Pitot tubes face into the direction of the pulley rotation. The rotational movement of the oil rams the oil into the pitot tubes, which direct the oil through a passage into and through the fan shaft and bracket, to an external oil outlet port (3). A line from the oil outlet port (3) carries the oil to a non-pressurized port on the engine where the engine oil is returned to the engine oil sump.