The 90º right angled thermostatic expansion valve has been used on vehicles since the early days of mobile air conditioning. There are two basic designs, internally and externally equalized valves, neither of which have seen many variations over the years. Although a reliable valve, the capillary tubes used for the temperature sensing bulb and the external equalizer can become kinked or broken. Damaged capillary tubes will make the valve inoperable. Many O.E. manufacturers have moved away from capillary tubed 90º valves and replaced them with H-type block valves or orifice tubes. However, the 90º valve is still used today on some automotive rear units and some heavy duty and agricultural vehicles.
Remote Bulb and Capillary Tube (Temperature Sensing Element)
Ball and Seat
External Equalizing Capillary Tube