GMC 22804122 Valve Assembly, A/C Evaporator Thermal Expansion

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There are multiple methods for converting high-pressure liquid refrigerant to lower-pressure vapor in air conditioning systems. This conversion occurs as the refrigerant passes through the evaporator, cooling the airflow for delivery to the vents. One common approach is to use a controlled orifice, which is often a removable component in the AC pipes at the firewall. However, the models covered in this manual utilize an A/C expansion valve (TXV) that serves the same purpose as a controlled orifice. To remove the front expansion valve, the air intake duct and windshield washer fluid heater (if present) must be taken out, followed by disconnecting the refrigerant lines from the TXV. If necessary, the power brake booster vacuum line should be disconnected and moved aside for better access. The TXV can then be removed by taking out the two bolts securing it to the firewall. For the rear auxiliary expansion valve, the passenger rear wheel and inner fender splash shield need to be removed first. From underneath the rear of the vehicle, the refrigerant lines should be disconnected from the rear auxiliary HVAC module by removing a single nut. Finally, the two bolts securing the TXV to the vehicle can be removed, allowing the valve to be taken out. When installing, all connections should be assembled with new O-rings or seals, lightly lubricated with R-134a refrigerant oil. The system should then be evacuated, charged, and leak tested.

One common approach is to use a controlled orifice, while another method is to use a thermostatic expansion valve (TXV).

To remove the front expansion valve, the air intake duct and windshield washer fluid heater (if present) must be taken out. Then, the refrigerant lines should be disconnected from the TXV. If necessary, the power brake booster vacuum line should be disconnected and moved aside for better access. Finally, the two bolts securing the TXV to the firewall can be removed.

The purpose of both the controlled orifice and the TXV is to convert high-pressure liquid refrigerant to lower-pressure vapor as it passes through the evaporator, cooling the airflow for delivery to the vents.