Reversing Valve Description And Operation - Friedrich Wallmaster WCT08A10A Service Manual

COMPONENT TESTING

Reversing Valve Description And Operation

The Reversing Valve controls the direction of refrigerant flow to the indoor and outdoor coils. It consists of a
pressure-operated, main valve and a pilot valve actuated by a solenoid plunger. The solenoid is energized during
the heating cycle only. The reversing valves used in the RAC system is a 2-position, 4-way valve.
The single tube on one side of the main valve body is the high-pressure inlet to the valve from the compressor.
The center tube on the opposite side is connected to the low pressure (suction) side of the compressor. The
other two are connected to the indoor and outdoor coils. Small capillary tubes connect each end of the main valve
cylinder to the "A" and "B" ports of the pilot valve. A third capillary is a common return line from these ports to the
suction tube on the main valve body. Four-way reversing valves also have a capillary tube from the compressor
discharge tube to the pilot valve.
The piston assembly in the main valve can only be shifted by the pressure differential between the high and low
sides of the system. The pilot section of the valve opens and closes ports for the small capillary tubes to the main
valve to cause it to shift.
NOTE: System operating pressures must be near normal before valve can shift.
B
A
Figure 702 (Reversing Valve)
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