What are the consequences of overfilling the air conditioning refrigerant oil in a car?
2 Answers
The consequences of overfilling the air conditioning refrigerant oil in a car are: it can cause excessive pressure in the condenser and insufficient pressure in the evaporator, and in severe cases, it can lead to blockage of the expansion valve or capillary tube. Refrigerant oil, also known as refrigeration oil, is used to lubricate the moving parts inside the refrigeration compressor. In the compressor, refrigerant oil primarily serves four functions: lubrication, sealing, cooling, and energy regulation. If the system is overfilled with oil, a portion of the oil cannot quickly and completely return to the compressor, forming an oil film in the evaporator and condenser, which affects heat dissipation and results in reduced cooling capacity. Currently, China produces five grades of refrigerant oil: No. 13, No. 18, No. 25, No. 30, and No. 40.
Last time I accidentally added too much refrigerant oil when servicing the air conditioning system myself, which significantly reduced the cooling performance. The air blowing out wasn't cold at all - it felt like hot air. This happened because refrigerant oil is meant to lubricate the AC compressor, but when overfilled, the excess oil occupies system space, reducing the amount of compressed refrigerant and decreasing heat exchange efficiency. The compressor also experiences increased resistance during operation with louder noise, and prolonged use may cause damage like oil seal failure or piston seizure. Later, I took it to a professional shop where the technician drained the excess oil and performed a precise refill, restoring normal system operation. This incident reminded me to be cautious with DIY vehicle maintenance - refrigerant oil quantity must follow manual specifications. Overfilling not only affects driving comfort in summer but could also lead to costly repairs. Having technicians check refrigerant oil levels during regular maintenance is crucial to avoid similar mistakes and maintain optimal AC performance.
