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.
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HOMESERVICE MANUALSSUBARU1998LEGACY BRIGHTON WAGON AWD F4-2.2L SOHCREPAIR AND DIAGNOSISHEATING AND AIR CONDITIONINGCOMPRESSOR HVACDESCRIPTION AND OPERATIONAIR CONDITIONING SYSTEMCOMPRESSORTRIGGER VALVE
1998 Subaru Legacy Brighton Wagon AWD F4-2.2L SOHC
Trigger Valve
1998 Subaru Legacy Brighton Wagon AWD F4-2.2L SOHCSECTION Trigger Valve
TRIGGER VALVE
This mechanism is designed to maintain proper vane back pressure to allow the vanes to move out with ease when the compressor starts. The trigger valve is provided in the side block, and a ditch called the K-ditch is provided in the side block rotor surface. The trigger valve has a ball combined with a spring. When vane chattering readily occurs like when the compressor starts or when the difference between the high and low pressures is small, spring action causes the valve to open to provide additional back pressure to the vanes, thereby assuring smooth operation.
1. When compressor starts or when load is low
When the compressor starts or when the load is low (the high pressure value is low), the trigger valve is opened by spring action to apply the pressure of the high pressure chamber to the back plane of vane to prevent vane chattering.
2. When compressor is in regular operation
When the pressure in the high pressure chamber of the compressor increases, the pressure difference closes the trigger valve against spring action. The oil port pressure of the side block is applied to the back plane of vane to maintain proper back pressure.
This mechanism is designed to maintain proper vane back pressure to allow the vanes to move out with ease when the compressor starts. The trigger valve is provided in the side block, and a ditch called the K-ditch is provided in the side block rotor surface. The trigger valve has a ball combined with a spring. When vane chattering readily occurs like when the compressor starts or when the difference between the high and low pressures is small, spring action causes the valve to open to provide additional back pressure to the vanes, thereby assuring smooth operation.
1. When compressor starts or when load is low
When the compressor starts or when the load is low (the high pressure value is low), the trigger valve is opened by spring action to apply the pressure of the high pressure chamber to the back plane of vane to prevent vane chattering.
2. When compressor is in regular operation
When the pressure in the high pressure chamber of the compressor increases, the pressure difference closes the trigger valve against spring action. The oil port pressure of the side block is applied to the back plane of vane to maintain proper back pressure.
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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.