General Motors FWD Models & Camaro & Firebird
All 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. All air conditioned vehicles are equipped with over-ride switches. These switches turn fan motor on whenever air conditioning system is operating, and return fan motor control to thermal relay when system is turned off.
Although all electric fans operate on same principle, the following are special descriptions that apply to specific models
Thermostatically Controlled Electric Fan. Scheme 1
Coolant temperature switch turns fan motor on at specified temeratures. Fan will also come on instantly when A/C is turned on. Fan motor shuts off when ignition switch is turned off, regardless of coolant temperature. The fan used on General Motors vehicles is 12" in diameter, made of plastic and has 5 blades.
If fan is not operating properly, disconnect fan motor wire connector and connect it with 14 gauge wire to a good 12-volt battery. If fan runs, motor is all right, indicating car battery, radiator fan switch (Chrysler), coolant relay, timer relay (Ford), coolant temperature switch (GM) or A/C relay (all models) may be defective. If fan motor does not run when connected directly to a good battery, replace fan motor.
Pontiac
This unit is a fixed blade assembly designed to flex the blades as the engine RPM increases. As RPM increases blade pitch decreases, thereby saving power and decreasing noise level. No adjustment or test is required beyond keeping the fan belt adjusted to the proper tension.
Flex Blade Fan Assembly. Scheme 2
All General Motors
Most air conditioned models use a thermostatically controlled fluid fan and torque control clutch. The thermal control drive is a silicone-filled coupling connecting the fan to the fan pulley, and is operated by a control valve. Control valve is operated by a temperature sensitive bimetal coil or strip and controls the flow of silicone through the clutch.
During periods of operation when radiator discharge air temperature is low, the fan clutch limits the fan speed. High radiator disharge air temperature causes bimetal to allow a greater flow of silicone to enter the clutch. This increases the drag between the driven member and driving member resulting in a higher fan speed and increased cooling.
TESTING
In cases of engine overheating or insufficient air conditioning proceed with the following tests
Scheme 3
- 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 the fan clutch engages. (Scheme 3): Thermostatically Controlled Fan Assembly NOTE: Shown with stamped face and bi-metal coil spring. NOTE: It will take approximately 5 to 10 minutes for the 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.
- As soon as the clutch engages, remove the radiator grille cover and turn the A/C off to assist in engine cooling.
- After several minutes the fan clutch should disengage. This can be determined by a reduction in fan speed and roar. If the fan fails to function as described, it should be replaced.