The four-way valve that swaps a heat pump between heating and cooling.
The reversing valve redirects compressor discharge either to the outdoor coil (cooling) or to the indoor coil (heating), swapping the roles of evaporator and condenser. A pilot solenoid, energized by O or B depending on the manufacturer, shifts it. A valve stuck in mid-position can let discharge gas bypass to suction, which looks like a weak compressor.
Exam work areas
F · Maintenance, service and troubleshooting