Best Practice: Bauteilwechsel mit der Spülfunktion

Replacing a component in a modern automotive A/C or heat pump system requires more than simply recovering the refrigerant, replacing the component and recharging the system.

The NUNCHI CLIMATE ACEntre20+, with its integrated refrigerant flushing function, allows the technician to perform a more complete repair procedure by helping remove old compressor oil, contamination and unwanted residues from suitable sections of the refrigerant circuit.

This is particularly important when replacing components following compressor failure, contamination, incorrect oil, system damage or major refrigerant-circuit repairs.

IMPORTANT: Always follow the vehicle manufacturer’s repair procedure. Refrigerant type, oil specification, oil quantity, flushing procedures, valve positions and component replacement requirements vary between vehicles.

1. IDENTIFY THE VEHICLE & SYSTEM

Before starting the repair, confirm:

• Vehicle make, model and year
• Refrigerant type
• Refrigerant charge quantity
• Compressor oil type
• Required oil quantity
• Conventional or electric compressor
• A/C or heat pump system
• Location and function of the component being replaced
• OEM-specific replacement procedure
• OEM flushing restrictions

Modern heat pump systems can contain multiple heat exchangers and electronically controlled valves. Understanding the refrigerant circuit before beginning the repair is essential.

2. DIAGNOSE BEFORE REPLACING

Before replacing a component, determine why the component failed.

Do not replace a component without investigating the root cause.

Check for:

• Refrigerant leakage
• Incorrect refrigerant charge
• Insufficient lubrication
• Excessive oil
• Incorrect compressor oil
• Moisture contamination
• Internal contamination
• Metal particles
• Restricted refrigerant flow
• Abnormal pressure
• Insufficient condenser/gas-cooler airflow
• Electrical problems
• Sensor faults
• Control-valve faults
• REPLACE THE CAUSE – NOT ONLY THE FAILED COMPONENT

A new component can fail again if the original cause remains in the system.

3. RECOVER THE REFRIGERANT

Connect the NUNCHI CLIMATE ACEntre20+ and perform a complete refrigerant recovery.

Allow the machine to complete the recovery cycle.

Record:

Specified refrigerant charge → Refrigerant recovered

A large difference can provide valuable diagnostic information and may indicate a leak, previous incorrect charging or refrigerant loss.

Never intentionally vent refrigerant to atmosphere.

4. INSPECT THE RECOVERED OIL

Pay particular attention to the oil removed during recovery.

Check for:

• Metal particles
• Dark discoloration
• Abnormal contamination
• Excessive oil
• Moisture
• Burnt or degraded oil
• Incorrect oil

The condition of the oil can provide important information about the internal condition of the system.

CONTAMINATED OIL = INVESTIGATE THE COMPLETE SYSTEM

If metal particles or significant contamination are present, do not assume the problem is limited to the component being replaced.

5. OPEN THE REFRIGERANT CIRCUIT SAFELY

After confirming that the refrigerant has been properly recovered, open the system according to the manufacturer’s procedure.

Keep the system open for the shortest possible time.

Moisture from ambient air can enter the refrigerant circuit and be absorbed by:

• Compressor oil
• Desiccant
• Internal component surfaces

Immediately cap or seal open hoses, pipes and components that are not being worked on.

CLEANLINESS IS CRITICAL

Never allow:

Dirt • Moisture • Dust • Metal particles • Incorrect oil • Workshop chemicals

to enter an open A/C or heat pump circuit.

6. INSPECT THE REMOVED COMPONENT

Do not immediately discard the old component.

Inspect it to help determine the reason for failure.

Look for:

• Metal particles
• Oil contamination
• Mechanical damage
• Internal blockage
• Seal failure
• Corrosion
• Abnormal oil condition

The failed component can provide valuable evidence about the condition of the rest of the refrigerant circuit.

7. DECIDE IF FLUSHING IS REQUIRED

Flushing is particularly important when contamination could remain inside the system after component replacement.

Consider flushing when:

• A compressor has mechanically failed
• Metal particles are present
• Compressor oil is contaminated
• Incorrect oil has been used
• Excessive oil is present
• Major components have been replaced
• The system has been contaminated
• The manufacturer requires flushing
• The objective is simple:
• DO NOT INSTALL A NEW COMPONENT INTO A CONTAMINATED SYSTEM.

8. IDENTIFY WHICH COMPONENTS CAN BE FLUSHED

Not every component is suitable for flushing.

Depending on the system and OEM instructions, components that may need to be isolated, bypassed or replaced include:

• Compressor
• Expansion valve
• Orifice tube
• Receiver drier
• Accumulator
• Desiccant
• Certain solenoid valves
• Electronic expansion valves
• Components containing very small internal passages

Some modern microchannel or parallel-flow heat exchangers can retain contamination that may be difficult or impossible to remove completely.

If reliable cleaning cannot be confirmed, component replacement may be required.

9. OPEN ELECTRONIC VALVES WHEN REQUIRED

Modern heat pump systems can contain several electronically controlled refrigerant valves.

Depending on the system design, a closed valve can prevent flushing refrigerant from reaching part of the circuit.

A compatible diagnostic scan tool may therefore be required to place valves in the correct service position.

Follow the vehicle manufacturer’s specified procedure.

A CLOSED VALVE CAN MEAN AN UNFLUSHED CIRCUIT.

This is particularly important when repairing modern hybrid and electric vehicle heat pump systems.

10. FLUSH WITH THE ACENTRE20+

Use the ACEntre20+ refrigerant flushing function according to the machine and vehicle manufacturer’s instructions.

Refrigerant is circulated through the appropriate section of the A/C circuit to help transport:

• Old compressor oil
• Contaminated oil
• Fine particles
• Suspended contamination
• Unwanted residues

out of the system.

One important advantage is that the flushing process uses refrigerant as the flushing medium, avoiding the need to introduce a separate flushing chemical into the sections being refrigerant-flushed.

11. EVALUATE THE FLUSHING RESULT

Monitor what is removed during the flushing process.

If contamination continues to be recovered, additional flushing may be necessary.

Do not judge the procedure only by the amount of time spent flushing.

FLUSH UNTIL THE REQUIRED CLEANLINESS IS ACHIEVED.

If the system cannot be cleaned adequately, identify and replace components that continue to trap contamination.

12. INSTALL THE NEW COMPONENT

Before installing the replacement component:

• Verify the correct part number.
• Check that the component is suitable for the refrigerant.
• Confirm oil compatibility.
• Keep protective caps installed until immediately before installation.
• Use new seals/O-rings where specified.
• Lubricate O-rings with the correct compatible oil where required.
• Use the correct tightening torque.
• Keep all connections clean.

Never reuse damaged or contaminated sealing components.

13. CORRECT THE OIL QUANTITY

This is one of the most important parts of component replacement.

Different A/C components can contain different amounts of compressor oil.

When replacing a component, determine how much oil:

was removed → remains in the system → was removed during flushing → is contained in the replacement component → must be added

Do not automatically add the system’s complete oil quantity unless the repair procedure specifically requires it.

TOO LITTLE OIL

Can cause:

• Poor compressor lubrication
• Increased wear
• Compressor overheating
• Premature compressor failure
• TOO MUCH OIL

Can cause:

• Reduced cooling performance
• Reduced heat-transfer efficiency
• Higher system pressures
• Oil accumulation in heat exchangers
• CORRECT OIL QUANTITY IS CRITICAL.

14. USE ONLY THE CORRECT OIL

Use only the oil specified by the vehicle or compressor manufacturer.

Depending on the application, this may include:

• PAG
• Double-end-capped PAG
• PAG YF
• POE
• PVE
• Other OEM-specified oil

Never mix oils simply because they have a similar viscosity.

EXTRA CARE WITH ELECTRIC COMPRESSORS

High-voltage electric compressors can require oil with specific electrical insulation properties.

Using the wrong oil or contaminating the system with another oil type can reduce electrical insulation resistance.

Maintain strict separation between oil types when servicing hybrid and electric vehicles.

15. REPLACE THE DRIER / DESICCANT WHEN REQUIRED

Following major system opening or component replacement, evaluate whether the:

• Receiver drier
• Accumulator
• Desiccant bag/cartridge

must be replaced.

The desiccant absorbs moisture entering the refrigerant circuit.

Flushing does not restore saturated desiccant.

Follow the vehicle manufacturer’s replacement requirements.

16. REASSEMBLE & CHECK THE SYSTEM

Before evacuation:

• Confirm all components are installed correctly.
• Check all refrigerant connections.
• Verify O-ring installation.
• Confirm correct tightening torque.
• Reconnect electrical connectors.
• Confirm all pipes and hoses are correctly routed.
• Return electronically controlled valves to the required service position.

Perform any OEM-required pressure or leak test before charging.

17. PERFORM A DEEP VACUUM

Use the ACEntre20+ to evacuate the system thoroughly.

The vacuum process is designed to remove:

• Air
• Moisture
• Residual refrigerant vapor
• Non-condensable gases

A system that has been open during component replacement may require a longer evacuation than a routine A/C service.

DO NOT SHORTEN THE VACUUM PROCESS TO SAVE TIME.

Moisture remaining in the system can affect oil, refrigerant and system reliability.

18. PERFORM THE VACUUM HOLD TEST

After evacuation, perform the appropriate vacuum hold/leak test.

Monitor for vacuum loss.

If the system does not maintain the required vacuum:

Do not recharge the vehicle and send it back into service.

Investigate the cause.

Remember that vacuum testing is only one part of leak verification and does not necessarily identify every possible leak.

19. CHARGE THE EXACT REFRIGERANT QUANTITY

Recharge the system with the manufacturer-specified refrigerant quantity.

Always charge according to weight.

Do not determine the final refrigerant quantity based only on pressure.

Modern A/C and heat pump systems can be highly sensitive to refrigerant charge.

UNDERCHARGED

Can result in:

• Poor cooling/heating
• Reduced compressor lubrication
• Abnormal operating conditions
• OVERCHARGED

Can result in:

• High pressures
• Reduced performance
• Increased compressor load
• Potential component damage
• 20. START & TEST THE SYSTEM

After charging, operate the A/C or heat pump system according to the vehicle manufacturer’s test conditions.

Allow the system to stabilize.

Check:

• High-side pressure
• Low-side pressure
• Vent temperature
• Ambient temperature
• Compressor operation
• Compressor noise
• Cooling fan operation
• Refrigerant flow
• Leak indications
• Fault codes

For heat pump systems, verify the appropriate cooling and heating operating modes.

21. CHECK FOR LEAKS

Pay particular attention to every connection disturbed during the repair.

Check around:

• New component
• Hose connections
• Pipe connections
• O-rings
• Service ports
• Compressor connections

Use the appropriate leak-detection method for the refrigerant and vehicle manufacturer’s procedure.

22. DOCUMENT THE REPAIR

Record the service information for future reference.

Recommended information includes:

• Component replaced
• Reason for replacement
• Refrigerant recovered
• Refrigerant charged
• Oil removed
• Oil added
• Oil specification
• Flushing performed
• Components flushed
• Drier/desiccant replacement
• Vacuum result
• Leak-test result
• Final pressures
• Final vent temperature
• Fault codes before/after repair