Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
2002 Subaru Outback VDC Sedan AWD F6-3.0LFACTORY OEM SERVICE PROCEDURE
Compressor Control System
Compressor Control System
GENERAL
1. When the A/C switch and fan switch are turned ON, the A/C relay is activated. The compressor starts operating, and then the main and sub fans also operate.
2. The thermo control amplifier, when activated, disengages the compressor clutch and the main and sub fans.
3. When the pressure switch turns on, the compressor clutch is disengaged and the main and sub fans also stop.
THERMO CONTROL AMPLIFIER
The thermo control amplifier disconnects the magnet clutch circuit to prevent the evaporator from becoming frosted when the temperature of the evaporator fin drops close to 3 °C (37 °F). When the limit temperature is reached, the thermistor (located on the evaporator fin) interrupts the base current of the amplifier. This deactivates the A/C relay, which in turn disconnects the magnet clutch circuit.
ACCELERATION CUT SYSTEM
The A/C switch turns the air conditioning system ON and OFF. The on-off signals from the switch are transmitted to the engine control module (ECM).
When the ECM receives a full-throttle signal from the throttle sensor during compressor operation, it deactivates the A/C relay to interrupt electric current to the compressor magnet clutch. This prevents the degradation of acceleration performance. The A/C relay is in the main fuse box located on the left side of the engine compartment.
IDLE SPEED CONTROL
The idle air control solenoid valve increases the engine idling speed when the compressor is in operation.
The engine control module activates the idle air control solenoid valve when it receives an A/C switch ON signal so that necessary by-pass air is introduced into the throttle body to ensure proper idling speed for an increased engine load.
FAN CONTROL
The main fan and sub fan are switched ON and OFF according to the operating modes as shown in the table.
GENERAL
1. When the A/C switch and fan switch are turned ON, the A/C relay is activated. The compressor starts operating, and then the main and sub fans also operate.
2. The thermo control amplifier, when activated, disengages the compressor clutch and the main and sub fans.
3. When the pressure switch turns on, the compressor clutch is disengaged and the main and sub fans also stop.
THERMO CONTROL AMPLIFIER
The thermo control amplifier disconnects the magnet clutch circuit to prevent the evaporator from becoming frosted when the temperature of the evaporator fin drops close to 3 °C (37 °F). When the limit temperature is reached, the thermistor (located on the evaporator fin) interrupts the base current of the amplifier. This deactivates the A/C relay, which in turn disconnects the magnet clutch circuit.
ACCELERATION CUT SYSTEM
The A/C switch turns the air conditioning system ON and OFF. The on-off signals from the switch are transmitted to the engine control module (ECM).
When the ECM receives a full-throttle signal from the throttle sensor during compressor operation, it deactivates the A/C relay to interrupt electric current to the compressor magnet clutch. This prevents the degradation of acceleration performance. The A/C relay is in the main fuse box located on the left side of the engine compartment.
IDLE SPEED CONTROL
The idle air control solenoid valve increases the engine idling speed when the compressor is in operation.
The engine control module activates the idle air control solenoid valve when it receives an A/C switch ON signal so that necessary by-pass air is introduced into the throttle body to ensure proper idling speed for an increased engine load.
FAN CONTROL
The main fan and sub fan are switched ON and OFF according to the operating modes as shown in the table.
Factory Service Tools
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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