Expansion valve, function - GF83.40-P-2123-01A
WARNING: This page does not describe the selected car, but rather 42 other vehicles, including the 1999 Mercedes-Benz S600, 1999 Mercedes-Benz S500, 1999 Mercedes-Benz S420, 1999 Mercedes-Benz S320, and 1999 Mercedes-Benz CL600. However, it is still accessible from the selected car via links, so may be relevant.
Function
When the A/C compressor is switched on the pressure in the evaporator decreases causing the diaphragm (1) to flex downward in an arch. The tappet (3) follows the motion of the diaphragm and presses the valve ball (4) away from its seat against the force of the spring (5). The refrigerant is sprayed into the evaporator through the open valve.
Since the motion of the diaphragm (1) is dependent on the intake pressure as well as the temperature at the evaporator output, only the quantity of refrigerant which can be evaporated optimally is injected.