Seville V8-300 4.9L (1991)
Radiator Cooling Fan Motor Relay: Description and Operation
The cooling system utilizes two plastic fans. The front fan is 12.2 inches (310 mm) in diameter and the rear fan is 16.20 inches (415 mm) in diameter.
The fans are driven by individual electric motors which are controlled electronically by the PCM/ECM. Fan speed is variable and is controlled based on
the engine coolant and A/C high-pressure refrigerant temperature.
Both fans are commanded ON with half power at a calibrated engine coolant temperature or A/C high refrigerant pressure threshold. Fan power increases
as engine temperature or refrigerant pressure increases and reaches full power at a higher calibrated engine coolant temperature or A/C high refrigerant
pressure. Undersirable on-off operation of the fans is eliminated by utilizing turn off temperatures lower than the turn on temperatures.
A cooling fan control module is no longer used on this vehicle. The module has been replaced by three relays, located in the relay center near the left
front fender shroud. Two of the relays operate in parallel at low fan speed, and in series at high fan speed. The third relay discriminates between the two
primary fan control relays.
