Century V6-3100 3.1L VIN M SFI (1998)
Voltage Signal: Description and Operation
Engine Cooling Fan Signal
Purpose
The electric cooling fans are used to lower the temperature of the engine coolant flowing through the radiator. They are also used to cool the
refrigerant (R134a) flowing through the A/C condenser.
Operation
Power for the fan motors is supplied through Cool Fan 1 Maxifuse(r) and Cool Fan 2 Maxifuse(r). The cooling fan relays are energized when current
flows from the fuses in the Underhood Electrical Center and through the relay coils to ground through the PCM. The Low Speed fans control circuit is
grounded for low speed fans operation. The Cool Fan 1 relay control circuit and the Cool Fan 2 and Cool Fan 3 circuits are all grounded for high
speed fans operation.
Low Speed Fans Operation
During low speed fans operation the PCM supplies a ground path for the Cool fan 1 relay. This closes the Cool Fan 1 relay contacts, allowing current
to flow from the 40 amp Cool Fan 1 Maxifuse(r) through the relay contacts to the Engine Coolant Fan Motor #1. During low speed operation, the
ground path for Engine Coolant Fan Motor #1 is through the Cool Fan 2 relay and the Engine Coolant Fan Motor #1. The result is a series circuit with
both cooling fans running at low speed.
High Speed Cooling Fan Operation
During high speed cooling fan operation the PCM supplies a ground path for the Cool Fan 1 relay. The PCM also supplies a ground path for Cool Fan
2 and Cool Fan 3 relay. This closes all three cooling fan relays. Engine Coolant Fan Motor #1 continues to receive current from the 40 amp Cool Fan
1 fuse. However, Engine Coolant Fan Motor #2 receives current from the 30 amp Cool Fan 2 fuse. During high speed operation each cooling fan has
its own ground path.
The PCM will complete the ground path for low speed cooling fan relay under any of the following conditions:
^
When engine coolant temperature exceeds 108°C (226°F).
^
When A/C is requested and ambient temperature is above 36°C (97°F).
^
When A/C refrigerant pressure is greater than 190 psi (2 volts).
^
When the ignition is off and engine coolant temperature is greater than 140°C (140°F).
The PCM will complete the ground paths for all engine three cooling fan relays under any of the following conditions:
^
When engine coolant temperature exceeds 113°C (235°F).
^
When A/C refrigerant pressure is greater than 240 psi (2.5 volts).
