Pressure Control Valve - Mechanical
A/C Demand High
During periods of moderate to high A/C demand, system suction pressure will be greater
than the control valve set point. During these periods, the control valve maintains a bleed
from crankcase to suction. Crankcase pressure is therefore equal to suction pressure. The
wobble plate angle, and therefore compressor displacement is at its maximum.
A/C demand low
During periods of low to moderate A/C demand, system suction pressure will decrease to
the control valve set point. The control valve maintains a bleed from discharge to crankcase
and prevents a bleed from crankcase to suction. The wobble plate angle, and therefore
compressor displacement is reduced or minimized. During these periods, displacement is
infinitely variable between approximately 5 and 100% of its maximum displacement
liquid
Automotive
bulb (3) is attached to the evaporator
outlet tube surface.
F2 - Pressure compensation tube
This is a hollow tube connected to the
evaporator outlet tube and senses the
pressure of the R134a refrigerant leaving
the evaporator coil. (Other TX valves may
not use this tube as pressure is provided
internally within the valve).
F3 - Pressure spring
This spring (6) is located under the ball
valve (5).