The principle upon which the 180 Solenoid Pilot Control influences the expansion valve action is by the creation of a pressure under the valve diaphragm which is higher than the bulb pressure. This is how it is accomplished. The type 180 has two parts, both in the the valve body-one high pressure and one low pressure. When the solenoid coil is energized, the plunger moves upward sealing off the high pressure port. With the high pressure excluded from the pilot control, true suction pressure acts on the underside of the expansion valve diaphragm through the equalizer line and the low pressure port. When the solenoid coil is de-energized, the low pressure port is closed, thereby closing the equalizer line from the valve to the suction line. The high pressure port is open and liquid line pressure is applied to the underside of the thermostatic expansion valve diaphragm. This high side pressure instantly overcomes the bulb pressure and supplements the valve spring, immediately closing the port of the expansion valve.