Expansion Valve, Basic Function - GF83.40-P-2018A

Model All (CAR) 

Example illustration of expansion valve 

Courtesy of MERCEDES-BENZ USA

Overview 

This document contains information on:

• General 
• Function 

General 

The expansion valve (1) sprays refrigerant into the evaporator. The injection quantity depends on the pressure and the temperature of the refrigerant supplied.

The expansion valve (1) is located at the rear of the engine compartment at the line passage to the vehicle interior. The installation location may vary depending on the model series.

Example illustration of expansion valve body 

Courtesy of MERCEDES-BENZ USA

Function 

When the air conditioning system is switched on, the pressure in the evaporator decreases, causing the diaphragm (1.1) in the aluminum housing (1.2) of the expansion valve (1) to arch. The diaphragm motion is transmitted to a plunger (1.3). The plunger (1.3) pushes a valve ball (1.4) out of its seat, thereby opening the expansion valve (1). The valve ball (1.4) is fed back into its seat via a spring (1.5).

The opened expansion valve (1) enables the refrigerant to be injected into the evaporator. The movement of the diaphragm (1.1) depends on both the suction pressure and the temperature at the evaporator outlet. This means that only the amount of refrigerant that can evaporate optimally is injected.