Subaru LEGACY 2002 Quick Reference Index page 489

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3. TRIGGER VALVE

This valve has a function of maintaining a proper level of pressure behind the vanes (vane back

pressure) such that they can move easily upon start of the compressor. The trigger valve is incor-

porated in the front side block and its end opens to a cavity called "K-ditch" that is provided in the

rotor side end of the side block. The valve consists of a check ball and a spring.

The vanes are prone to chatter if there is only small difference between the high- and low-pres-

sures. This condition typically occurs when the compressor is started. In such a condition, the

spring raises the ball to open the valve and allows the back pressure to act on the vanes, thereby

ensuring smooth operation.

(2) Check ball

1) When compressor starts or when load is low:

When the compressor starts or when the load is low (the high-pressure level is low), the spring

can raise the check ball clear of its seat, so the trigger valve is opened. The pressure of the high-

pressure chamber then acts on the back end surface of each vane to prevent it from chattering.

(1) High-pressure chamber

(2) Trigger valve (Open)

(3) Front head

HVAC System (Heater, Ventilator and A/C)

Chapters

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