To facilitate assembling of a refrigerant system and to effectively seal a refrigerant in a filter/dryer assembly having a thermal expansion valve used for an automotive air conditioning system.

The filter/dryer 10 has a valve block 20 integral with a header 16 welded to a canister 14 for containing a desiccant and a filter material 36. The block 20 has a bore 22 for charging a heat responding cartridge valve. Since the valve is previously calibrated and charged in the bore 22 after welding the header 16 and the block 20, it is not exposed with a heat during welding. A refrigerant is fed from an evaporator to a compressor through a communicating passage 40, and hence the cartridge valve can be opened or closed in response to its temperature.