Expansion Valve: Description and Operation

The rear air conditioning system uses a Thermal Expansion Valve (TXV). The valve consists of the capillary tube, body, actuating pins, seat and orifice. At the high pressure liquid inlet, a fine mesh screen prevents dirt, filings or other foreign material from entering the valve orifice.

When the valve is connected in the system, high pressure liquid refrigerant enters the valve through the screen from the condenser and passes on to the seat and orifice where it changes into a low pressure liquid.

The low pressure liquid leaves the valve and flows into the rear evaporator core where it absorbs heat from the rear evaporator core and changes to a low pressure vapor and leaves the rear evaporator core. The capillary tube is clamped to the low pressure vapor line just below the outlet of the rear evaporator. The capillary tube is held in contact with the rear evaporator outlet tube by a metal clip placed near the end of the tube.