THERMOSTATICALLY CONTROLLED ELECTRIC FAN
Electrically-driven fans are actuated by thermal relay switches. Thermal switches turn fan motor on when necessary and shut fan motor off when not needed. Air conditioned vehicles are equipped with over-ride switches. These switches turn fan motor on whenever air conditioning system is operating. When system is turned off, fan motor control is returned to thermal relay. (Scheme 4)
Scheme 4
This unit is a flexible blade assembly designed to flex blades as engine RPM increases. As RPM increases, blade pitch decreases, thereby saving power and decreasing noise level. Keep fan belt adjusted to proper tension as necessary.
VARIABLE SPEED COOLING FAN CLUTCH (THERMOSTATIC CONTROL)
Most air conditioned models use a thermostatically controlled fluid fan and torque control clutch. Thermal control drive is a silicone-filled coupling connecting fan to a fan pulley, and is operated by a control valve. Control valve is operated by a temperature sensitive bi-metallic coil or strip and controls flow of silicone through the clutch.
During periods of operation when radiator discharge air temperature is low, fan clutch speeds are slowed, decreasing load on fan belt. High radiator discharge air temperature causes bi-metallic coil or strip to allow a greater flow of silicone to enter clutch. This increases drag between driven member and driving member resulting in a higher fan speed and increased cooling. (Scheme 5)
Thermostatically Controlled Fan Hub Assembly. Scheme 5
900 Model
The cooling fan, located behind the radiator, is thermostatically controlled by the coolant temperature switch (39) located at the top left of the radiator. A coolant fan time delay relay (26) is used. (Scheme 6)
9000 Model
The supply is taken from fuse 23 to temperature switch 39, regardless of the position of the ignition switch. When the engine coolant temperature has reached 92°C, the temperature switch will close and radiator fan 37 will start. (Scheme 7)
TIME-DELAY RELAY
Certain models are equipped with a time delay relay that limits the running time of the radiator fan after the engine is stopped. Relay 26 is always energized when the engine is running, i.e. when the ignition switch is in the ON position. The fan is controlled by switch 39. If the engine is stopped, the +15V supply to the relay coil will be disconnected. After about 10 minutes, the relay will disconnect the fan motor supply even if temperature switch 39 is closed. See WIRING DIAGRAMS .
Disconnect fan motor wire connector and connect it with 14-gauge wire to a good 12-volt battery. If fan runs, motor is okay. This indicates car battery, thermal switch, radiator fan switch, coolant relay, timer relay, coolant temperature switch, or A/C relay may be defective. If fan motor does not run when connected directly to a good battery, replace fan motor.
ENGINE OVERHEATING OR INSUFFICIENT AIR CONDITIONING
- Start with a cool engine to ensure complete fan clutch disengagement.
- Cover radiator grille sufficiently to induce high engine temperature.
- Start engine and operate at 2000 RPM. Turn on air conditioning if equipped.
- A fan roar will be noticed when fan clutch engages. NOTE: It will take approximately 5 to 10 minutes for temperature to become high enough to allow engagement of the fan clutch. While operating engine under these conditions, observe temperature light to prevent overheating. If HOT light comes on, remove cover from radiator grille.
- When clutch engages, remove radiator grille cover and turn A/C off to assist in engine cooling.
- After several minutes fan clutch should disengage. This can be determined by a reduction in fan speed and roar. If fan fails to function as described, it should be replaced.
Note. To avoid premature cooling system wear, always use the manufacturer's recommended coolant products and coolant mixture ratios.
FAULT-TRACING HINTS (ELECTRICAL)
Refer to WIRING DIAGRAMS to check the following items
- Check the fuses.
- Check the coolant fan time delay relay (26) by checking for voltage at the relay panel sockets (terminals 30 and 87).
- Check the coolant temperature switch by jumpering the switch terminals with the key on. The fan should now run.
- Check connectors, wiring and ground connections.
Scheme 6
Scheme 7
See also:
• WIRING DIAGRAMS