Expansion valve is a heat exchanger. It is located in the car directly under the control panel. In case of failure the valve may be in several positions: open, closed and narrowed. Expansion valve is a device to regulate the value of the coolant entering the evaporator. The expansion valve is placed after the drier filter on the evaporator inlet. It reduces the pressure and temperature of the coolant. Calibration orifice lowers the pressure of the fluid which enters the valve. The coolant, which comes from the drier filter, is like a fluid under high pressure. Passing through the hole of the thermostatic valve, the coolant is sprayed. In this process the pressure and temperature of the coolant is reduced to ensure its evaporation and to enhance heat transfer when passing through the evaporator. Thus, further evaporation of the coolant in the evaporator is provided.

How does the process of coordination of the running of the coolant flowing through the expansion valve occur? Thermal sensor cylinder is in direct thermal contact with the exhaust pipe evaporator. Deep inside the capacity of the capillary tube and the bellows there is gas - coolant R12. The bottom of the bellows rapidly presses the ball or needle, which is moving and increases the flow of coolant passing through the expansion valve, causing a decrease of temperature of the output tube and evaporator. Coolant’s R12 pressure in the sensor is reduced. The bellows is compressed, the ball covers the coil, causing at the same time coolant flow reducing.

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AC Expansion Valve for AUDI ALLROAD (4BH, C5), VOLVO V70 I (LV), MITSUBISHI CARISMA (DA_)

• the valve temperature sensor failure;
• violation of liquid refrigerant pressure;
• damage to the cylinder;
• needle jamming;
• damage to the spring.

• random shutdown of the compressor;
• unstable operation of the cooling system;
• low level of forward and suction pressure;
• too high refrigerant level supplied to the evaporator;
• frosting on the evaporator tubes;
• the valve being in an open state for a long period;
• systematic cooling air bleed.

• incorrect adjustment of the valve;
• blockage of the valve;
• moisture;
• mechanical damage;
• air getting into the air conditioning system.

For troubleshooting check the pressure change. You should use equipment, which is designed for operating with refrigerant. Connect the station to the socket. Then remove the glove box, install pressure gauges. Then connect two thermometers: near the intake duct and the central grid. Then, open the hood and front doors, run the air conditioner at maximum capacity, set the engine speed to 1,500 rpm. After 10 minutes of operation in this mode it is necessary to take the readings of thetemperature and pressure gauges. Too low or high pressure indicates a malfunction of the valve. Then perform a visual inspection of the expansion valve for the presence of ice and dirt.

Repair of the expansion valve is its washing from contaminants. If there are other faults the part is replaced. To do this, remove the glove box and the evaporator. If necessary, make gas recovery in the station. Then you need to remove the valve, install a new part, pre-lubricated with oil. Install the seals in the reverse order, reinstall the parts.