Expansion valve, function - GF83.40-P-2123-01P
WARNING: This page is about a different car, the 2009 Mercedes-Benz E550 and 2008 Mercedes-Benz E550. However, it is still accessible from the selected car via links, so may be relevant.
When the refrigerant compressor is switched on the pressure in the evaporator drops, thereby causing the diaphragm (1) to curve downwards. The tappet (3) follows the diaphragm movement and presses the valve ball (4) against the spring (5) away from its seat. The opened valve enables the refrigerant to be sprayed into the evaporator.
As the diaphragm movement (1) is dependent on both the intake pressure and the temperature at the evaporator outlet, only the specific quantity of refrigerant, as required for optimum vaporization, is injected.