A/C compressor replacement: flushing, oil and evacuation

Decide whether it really needs replacing

Before replacement

• Recover the refrigerant; never vent it to atmosphere.
• Confirm the refrigerant: R134a and R1234yf are not interchangeable.
• Confirm the oil type and quantity from the manual.
• Check the old oil colour and debris to judge contamination.

Standard sequence

• Recover the refrigerant.
• Remove the compressor and drain the old oil for inspection.
• Flush the circuit as the manufacturer requires; some components cannot be flushed and must be replaced.
• Replace the receiver-drier or accumulator; replace the expansion valve or orifice tube if contamination is heavy.
• Add the specified oil type and quantity.
• Renew O-rings and seals.
• Evacuate and hold a vacuum to check for leaks.
• Charge the specified refrigerant quantity and check high/low pressures and vent temperature.

Oil and refrigerant quantity

Follow the manual: too much oil reduces heat transfer, too little starves lubrication; too much refrigerant raises pressure and cuts cooling, too little reduces capacity.

When a dryer, hose or other component is replaced, the oil quantity must be compensated as the model instructions state.

Common mistakes

• Not replacing the dryer.
• Skipping evacuation or evacuating for too short a time.
• Mixing refrigerants or oils.
• Incomplete flushing, leaving debris in the circuit.
• Topping up refrigerant without finding the leak.

Safety

Refrigerant requires recovery equipment; liquid refrigerant and PAG oil can cause cold burns or skin irritation; keep the area ventilated and away from open flame.