Expansion Valve: Description and Operation

GF83.40-P-2190RI Expansion Valve, Component Description

Component Identification:

Location
The expansion valve is located at the rear left in the engine compartment, next to the brake booster.

Task
The expansion valve sprays liquid refrigerant into the evaporator. The injection quantity depends on the pressure and temperature of the refrigerant supplied.

Design
The expansion valve primarily consists of the following components:
- Diaphragm (a)
- Aluminum housing (b)
- Tappet (c)
- Valve ball (d)
- Spring (e)

Function
When the refrigerant compressor is switched on (A9), the pressure drops in the evaporator. This causes the diaphragm in the expansion valve to bulge. The diaphragm motion is transferred to a plunger. The plunger presses the valve ball out of its seat opening the valve. The opened valve enables the refrigerant to be sprayed into the evaporator. Because the motion of the diaphragm depends on the suction pressure as well as the temperature at the evaporator outlet, only the quantity of refrigerant which can evaporate optimally is injected.