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Services > Air Conditioning & Heating> Air Conditioning System Parts > AC Expansion Valve
Function: The restriction point at which the refrigerant expands and cools. (Vehicles are equipped with either an expansion valve of an orifice tube)
Signs of Wear: Lack of cooling within the vehicle cabin.
Air Conditioning Component: AC Expansion Valve- Houston's Premier Auto Repair Facility
The expansion valve represents the point of separation between the high pressure and low pressure sections in the refrigerant circuit. It is installed upstream of the evaporator. To achieve optimum cooling capacity in the evaporator, the refrigerant flow is controlled by the expansion valve depending on the temperature. As a result, complete evaporation of the liquid refrigerant is ensured and gaseous refrigerant arrives at the compressor only. Expansion valves may differ in their design.
How they work
The liquid refrigerant - arriving through the filter dryer from the condenser - flows through the expansion valve and is injected into the evaporator. The evaporating refrigerant releases evaporation cold. This causes temperature to drop. To achieve optimum cooling capacity in the evaporator, the refrigerant flow is controlled by the expansion valve depending on the temperature. At the end of the evaporator, the refrigerant is transported through the expansion valve to the compressor. If the refrigerant temperature increases at the end of the evaporator, it expands in the expansion valve. This results in an increase of the refrigerant flow (injection quantity) to the evaporator. If the refrigerant temperature lowers at the end of the evaporator, the volume in the expansion valve decreases. As a result, the expansion valve reduces the refrigerant flow to the evaporator.
Effects of failure
A defective expansion valve can manifest itself as follows:
- Poor cooling capacity
- Failure of the air conditioning system
There are a number of possible causes of failure:
- Temperature problems due to overheating or icing
- Contaminants in the system
- Leaks at the component or connection pipes