A solenoid directional valve works based on the attractive force of an electromagnet. When the electromagnet is energized, the armature's attractive force pushes the spool to move within the valve body. When power is cut, the spool returns to its original position by the action of a spring.

Directional control valves are used in hydraulic systems to precisely control the flow of hydraulic oil. They achieve directional control of fluid by diverting it in different directions. Fluid can be routed from the source to an actuator, or from an actuator to the return line. This allows for controlling the movement of hydraulic cylinders or hydraulic motors in different directions.

The two primary characteristics to consider when selecting a directional control valve are the number of fluid ports and the number of directional states (or positions) the valve can achieve. Valve ports provide channels for hydraulic fluid to flow to or from other components. The number of positions refers to the number of different flow paths the valve can offer.

If the valve gets stuck, it will be unable to switch from a heating to a cooling position, or vice versa. A faulty solenoid coil can lead to a lack of power in cooling mode. Internal valve leakage is difficult to troubleshoot and is often confused with insufficient compressor pumping capacity. Symptoms of directional valve leakage and compressor failure are the same: a reduction in the system's heating and cooling capacity. This is because the compressor continuously pumps gas internally through the leaking valve, leading to a loss of available cooling.

• Regularly clean and replace filters as needed.
• Check the oil for water (cloudy appearance), air (foaming in the oil), or burnt oil (rancid smell). Correct as needed.
• Regularly check the tank oil level. Add oil as needed.