3.0L CATERA: Description

Auxiliary Fans Low Speed, Electric Cooling Fan Low Speed

Battery voltage is supplied to heater water auxiliary pump whenever ignition switch is on. When engine temperature reaches 212°F (100°C), primary cooling fan temperature switch stage 1 will close, enabling fan control relay K26 to energize. When fan control relay K26 energizes, battery voltage from fuse 52 is applied to auxiliary coolant fan 1 (auxiliary engine coolant fan 1 is wired in series with auxiliary engine fan 2, through normally closed contacts of fan control relay K52. This will cause auxiliary coolant fans 1 and 2 to operate at low speed. Fan control relay K26 will also supply battery voltage to engine coolant fan resistor, voltage passes through resistor to electric coolant fan. Engine coolant fan resistor will cause engine coolant fan to operate at low speed. Primary cooling fan temperature switch stage 1 contacts will open when coolant temperature reaches 203°F (95°C). This will turn all 3 fans off, unless air conditioning system is on.

Auxiliary Fans High Speed

When engine temperature reaches 221°F (105°C), secondary cooling fan temperature switch contacts will close and energize fan control relays K52 and K28. When fan control relay K52 energizes, it will ground terminal "B" of auxiliary engine coolant fan 1. Terminal "A" of auxiliary engine fan 1 still receives battery voltage from fan control relay K26. Auxiliary coolant fan 1 is no longer in series with auxiliary engine coolant fan 2 and will now operate at full speed. When fan control relay K28 is energized, battery voltage from fuse 40 will be applied to terminal "A" of auxiliary engine coolant fan 2. Auxiliary coolant fan 2 is no longer in series with auxiliary engine coolant fan 1 and operates at full speed. Terminal "B" of auxiliary coolant fan 2 is permanently grounded. With stage 1 contacts of primary cooling fan temperature switch closed, electric cooling fan will continue to operate. Secondary cooling fan temperature switch contacts will open when coolant temperature reaches 212°F (100°C). This will cause auxiliary engine coolant fans 1 and 2 to operate at low speed.

Electric Coolant Fan High Speed

When engine coolant temperature reaches 230°F (110°C), primary cooling fan temperature switch stage 2 will close energizing fan control relay K67. When fan control relay K67 energizes, battery voltage from fuse 42 will be applied directly to terminal "A" of engine coolant fan (bypassing engine coolant fan resistor ) and engine coolant fan will operate at full speed. All other operations that were taking place before coolant temperature reached 230°F (110°C) will remain in effect. Primary cooling fan temperature switch stage 2 contacts will open when coolant temperature reaches 221°F (105°C) and primary engine coolant fan will shut off. At coolant temperatures above approximately 230°F (110°C), all 3 coolant fans are operating at full speed. Only 5 of 6 relays operate at this time, unless air conditioning system is turned on. In this case, fan control relay K87 and A/C compressor relay K60 will also operate.

Engine Cooling Fans (A/C Operation)

When A/C compressor is turned on, fan control relay K87 is energized and auxiliary engine coolant fans 1 and 2 will operate in low speed. In order to prevent inadmissible high refrigerant pressure in refrigerant circuit, auxiliary engine coolant fans 1 and 2 are switched from low speed to high speed at refrigerant pressures above approximately 275 psi. When pressure drops less than about 217 psi, auxiliary engine coolant fans 1 and 2 are switched back to low speed.

Water Auxiliary Pump

When ignition is off and engine coolant temperature reaches 212°F (100°C), primary cooling fan temperature switch stage 1 will close, enabling fan control relay K26 to energize. When fan control relay K26 energizes, battery voltage from fuse 52 is applied through normally closed auxiliary water pump relay K22, allowing water auxiliary pump to operate. Fan control relay K26 will also supply battery voltage to engine coolant resistor, allowing voltage to pass through resistor to electric cooling fan. Engine cooling fan resistor will cause engine cooling fan to operate at low speed. When engine coolant temperature reaches 203°F (95°C), primary cooling fan temperature switch stage 1 will open, de-energizing fan control relay K26. This will turn water auxiliary pump and engine cooling fan off.