Cooling System: Description and Operation

Voltage is provided at all times to the radiator fan relay contacts through fuse 57 and to the condenser fan relay contacts through fuse 58. With the ignition switch ON (II), voltage is provided to the coils of the condenser, radiator, and radiator fan main relays through fuse 3 (in the driver's under-dash fuse-relay box).

Low Speed

The coil of the condenser fan relay is grounded under one of the following conditions: (1) When the A/C is ON and the refrigerant pressure is above 220 psi (1,520 kpa) in which ground is provided by the Heater Control Panel (LX) or Climate Control Unit (EX, EX-L) or (2) When the engine coolant temperature is more than 199°F (93°C) but less than 210°F (99°C) and the A/C is not ON, thus closing radiator fan switch A and grounding at G101. Grounding the condenser fan relay energizes the coil and applies battery voltage to the condenser fan motor. Since the fan control relay is not energized, the condenser and radiator fan motors are in series with each other and grounded at G201. Both fans run at a reduced speed until ground is removed from the condenser fan relay.

High Speed

All the relays are grounded under any one of the following conditions: (1) When the radiator fan switch B closes [engine coolant temperature is more than 210°F (99°C)] or (2) When the PCM grounds terminal A20 ('99-00, '02-03) or E13 ('01) or (3) When the A/C is ON and the refrigerant pressure is above 220 psi (1,520 kpa) closing the A/C pressure switch. Grounding the relays energizes their coils and applies battery voltage to the radiator and condenser fan motors. The radiator fan is grounded at G201 and the condenser fan is grounded through the closed radiator fan main relay contacts to G201. Both fans will run at full speed until ground is removed from the relays.

When the refrigerant pressure is below 28 psi (196 kpa) or above 455 psi (3,140 kpa) the A/C pressure switch opens the circuit to the A/C switch and stops the air conditioning to protect the compressor.