The receiver drier is the part of your car’s air conditioning system that removes moisture from the refrigerant in order to prevent corrosion in the A/C system. It also filters out items that cannot condense and maintains some refrigerant in a liquid state for proper pressurizing.
When anything goes wrong with the A/C system, such as a leak, a loss of pressure, or a broken component, it’s very likely that the receiver-drier is also compromised. This highly sensitive filter should be replaced anytime maintenance or repair is done to the A/C system. Many mechanics and some manufacturers recommend that the receiver-drier be replaced on a routine basis whether the A/C needs repair or not.
This replacement is because the drying part of the receiver-drier, the dessicant pellets, can become saturated over time or when air enters the system, allowing moisture to stay in the system. Moisture (water) can combine with refrigerant under pressure to form hydrochloric acid, which is highly corrosive.