AC Compressor

Replacing an AC compressor is a major repair, so it can be frustrating when the replacement compressor fails soon afterwards.

A new compressor does not always fail because the replacement part itself is defective. Sometimes, the original compressor failure has left contamination, incorrect system conditions or another underlying problem that has not been addressed.

If the cause of the original failure is still present, installing another compressor may only lead to the same problem happening again.

This guide explains some of the most common causes of compressor failure after replacement and what should be considered before fitting another compressor.

Why Can a New AC Compressor Fail?

An automotive air conditioning system is made up of several components that need to work together under the correct operating conditions.

When a compressor fails internally, the failure can affect more than the compressor itself. Contamination may circulate through the refrigerant circuit, while other problems such as incorrect oil, excessive pressure, refrigerant charge issues or restricted components can also affect the replacement compressor.

Common causes include:

• Contamination and metal debris
• Moisture inside the system
• Incorrect refrigerant oil or oil quantity
• A blocked or restricted condenser
• Incorrect refrigerant charge
• Excessive system pressure
• Problems with the expansion valve or orifice tube
• Debris remaining in refrigerant lines or other components

The important point is that the cause of the original failure needs to be considered before installing another compressor.

For an overview of the warning signs that may indicate a compressor problem, read our guide to the common signs of a failing car AC compressor.

1. Contamination and Metal Debris

One of the most important things to check after an internal compressor failure is contamination.

When an AC compressor suffers an internal mechanical failure, metal particles and contaminated oil can be distributed through the refrigerant circuit.

These contaminants can remain in components such as the refrigerant lines, condenser, expansion valve or orifice tube, evaporator and other parts of the system.

If contamination is left in suitable components that are reused, it can circulate back through the system and reach the replacement compressor. This can cause rapid wear or premature failure.

The risk is particularly important after a significant internal compressor failure, where contamination may have spread beyond the compressor itself.

This is why replacing the compressor alone may not be enough.

2. Moisture Inside the AC System

Moisture can also affect the condition and reliability of an automotive AC system.

The receiver drier or accumulator contains desiccant that helps control moisture inside the system. However, once an AC system has been opened, moisture can enter from the atmosphere.

Moisture can contribute to corrosion and can also react with refrigerant and oil under certain conditions, contributing to acid formation and damage over time.

Proper system evacuation is therefore an important part of preparing the system after it has been opened.

3. Incorrect Refrigerant Oil

Refrigerant oil provides lubrication for the compressor, so using the correct oil is important for reliable operation.

Problems can occur if the wrong oil type or viscosity is used, or if the total oil quantity is incorrect.

When a compressor or other AC components are replaced, the technician may need to consider:

• The specified oil type and viscosity
• The total system oil capacity
• The amount of oil already contained in the replacement compressor
• The oil requirements associated with other replaced components
• The vehicle and compressor manufacturer's installation procedure

It is therefore not safe to assume that every replacement compressor needs the same amount of additional oil.

Too much oil can affect cooling performance and compressor operation, while too little oil can reduce lubrication and increase internal wear.

4. A Blocked or Restricted Condenser

The condenser removes heat from the refrigerant before it returns through the rest of the system.

If the condenser is internally restricted, contaminated or otherwise unable to operate correctly, refrigerant flow and system pressures can be affected.

After a compressor failure, contamination may also remain inside the condenser.

Some modern condenser designs can be difficult to clean thoroughly, particularly after severe contamination. In these situations, flushing may not be enough and the condenser may need to be replaced.

This is one reason the condition of the condenser should be considered when diagnosing a repeat compressor failure.

Related guide: Learn more about the signs of a blocked or restricted AC condenser.

5. Incorrect Refrigerant Charge

Automotive AC systems are designed to operate with a specified refrigerant type and charge.

Both undercharging and overcharging can affect system performance and compressor reliability.

An incorrect refrigerant charge can create abnormal operating conditions and may contribute to excessive compressor load or other system problems.

The system should therefore be recharged using the refrigerant specified for the particular vehicle and the manufacturer's specified charge weight, rather than estimating the amount.

6. Excessive System Pressure

High system pressure can place additional load on the compressor.

There can be several reasons for abnormal pressure, including an incorrect refrigerant charge, condenser restrictions, poor condenser airflow or other problems affecting heat rejection.

If the system pressure is outside the expected range, the cause should be investigated rather than simply replacing the compressor again.

A replacement compressor cannot correct a pressure problem elsewhere in the AC system.

7. Expansion Valve or Orifice Tube Problems

Depending on the vehicle, the AC system may use an expansion valve or an orifice tube to control refrigerant flow.

These components can be affected by contamination or debris following certain types of compressor failure.

If contamination has entered the system, the expansion valve or orifice tube should be considered as part of the inspection.

Whether the component needs to be replaced or otherwise dealt with depends on its condition and the applicable repair procedure.

8. Debris Remaining in Refrigerant Lines and Other Components

Contamination can remain in more places than just the compressor.

Metal particles, contaminated oil and other debris can stay inside refrigerant lines and other components after a compressor failure.

If they are not adequately removed, they can circulate through the system when the new compressor starts operating.

This is why a compressor replacement should be treated as part of a wider AC system repair when the original failure involved internal contamination.

Should You Flush the AC System When Replacing a Compressor?

Not every compressor replacement requires the same flushing procedure.

If an internal compressor failure has contaminated the refrigerant circuit, suitable reusable components should be flushed using the appropriate equipment and procedure.

The purpose of flushing is to remove contaminated oil and debris from components that can be safely and effectively cleaned.

However, flushing does not guarantee that every component can be completely cleaned.

Some components may be difficult or impossible to flush effectively, particularly after severe contamination. Depending on the component and the vehicle, replacement may be the better option.

The receiver drier or accumulator is one example of a component that is not simply cleaned by flushing. Its desiccant is intended to absorb moisture, and the component is normally replaced rather than flushed when replacement is required.

Should the Receiver Drier or Accumulator Be Replaced?

Often, yes.

After the AC system has been opened, or following an internal compressor failure, the receiver drier or accumulator will commonly need to be replaced, depending on the vehicle and manufacturer's procedure.

These components contain desiccant that helps absorb moisture. They can also be affected by contamination following a compressor failure.

Replacing the appropriate component can help reduce the amount of moisture or contamination left in the system before the replacement compressor is installed.

Pull a Proper Vacuum Before Recharging

Before refrigerant is added, the AC system should be properly evacuated using a vacuum pump.

A proper evacuation helps remove air and non-condensable gases and reduces moisture inside the system.

Evacuation does not guarantee that every trace of moisture has been removed, but it significantly reduces moisture remaining in the system.

Moisture left inside the system can contribute to corrosion and acid formation and may affect component reliability over time.

Skipping or inadequately performing the evacuation process can therefore affect both system performance and compressor reliability.

The appropriate evacuation procedure should follow the requirements for the particular vehicle and service equipment.

Recharge With the Correct Refrigerant

After evacuation, the system needs to be charged with the correct refrigerant type and quantity.

The refrigerant specification should be confirmed for the particular vehicle rather than assumed based only on the vehicle's age or model.

Professional workshops should charge the system according to the manufacturer's specified refrigerant weight.

Accurate charging helps the AC system operate within its intended conditions and reduces the risk of problems caused by an incorrect refrigerant charge.

What Should Be Checked Before Installing Another Compressor?

Before fitting another compressor after a failure, the first question should be:

Why did the original compressor fail?

Depending on the failure, the workshop may need to inspect for contamination, check the condenser and other related components, confirm the correct oil, replace the receiver drier or accumulator where required, evacuate the system and recharge it with the correct refrigerant.

The aim is not to replace every component automatically. It is to identify the conditions that could have caused or contributed to the original failure and address them before the replacement compressor is put into service.

This approach can help reduce the risk of another premature failure.

Does a New Compressor Failure Always Mean the Compressor Was Defective?

No.

A replacement compressor can fail because of a product-related fault, but it can also be affected by problems elsewhere in the AC system.

For example, contamination left after an internal compressor failure, incorrect oil, excessive pressure, an incorrect refrigerant charge or a restricted component can all affect compressor reliability.

That is why a second compressor failure should be properly assessed before assuming that the replacement part itself was defective.

The same principle applies whether the replacement compressor is OEM or aftermarket.

Why Does Installation Matter?

Installing a replacement compressor is more than simply removing the old unit and fitting the new one.

The condition of the existing AC system needs to be considered, particularly when the original compressor failed internally.

Correct oil, system preparation, evacuation and refrigerant charging all matter. Contaminated or restricted components may also need to be cleaned, inspected or replaced.

A quality replacement compressor cannot correct an unresolved problem elsewhere in the system.

What If the Replacement Compressor Fails Again?

If a replacement compressor fails shortly after installation, the cause should be investigated before another compressor is fitted.

The assessment may need to consider the original failure, contamination, oil, refrigerant charge, system pressure and the condition of related components.

If the compressor is covered by a supplier warranty, the relevant purchase and installation records should also be kept for the warranty assessment.

For more information about aftermarket compressor warranties and what can affect a warranty claim in Australia, see our guide:

Does an Aftermarket AC Compressor Void Your Car Warranty in Australia?

Frequently Asked Questions

Can a new AC compressor fail shortly after installation?

Yes.

A replacement compressor can fail prematurely if contamination, incorrect oil, excessive pressure, an incorrect refrigerant charge, restrictions or other unresolved system problems remain.

A product-related fault is also possible, so the cause of the failure should be properly assessed.

Should the AC system always be flushed when replacing a compressor?

No.

Flushing depends on the type and severity of the compressor failure and the design of the AC system.

Suitable reusable components may need to be flushed when contamination is present, while some components may need to be replaced because they cannot be adequately cleaned.

Should the receiver drier or accumulator be replaced?

It will commonly need to be replaced after the system has been opened or following an internal compressor failure, depending on the vehicle and manufacturer's procedure.

These components contain desiccant and are generally not cleaned by flushing.

Does a new AC compressor come with the correct amount of oil?

Not necessarily.

The oil already contained in a replacement compressor and the amount required for the vehicle can vary.

The correct oil type and quantity should be confirmed using the vehicle and compressor manufacturer's procedure.

Can an aftermarket compressor fail because of the AC system?

Yes.

Contamination, incorrect oil, excessive pressure, an incorrect refrigerant charge or other unresolved system problems can affect a replacement compressor.

These conditions can affect OEM and aftermarket compressors alike.

What should I check if a replacement compressor fails again?

The cause of the original failure should be investigated first.

The workshop may need to check for contamination, inspect related components, confirm the oil and refrigerant specifications, check system pressures and make sure the system was properly evacuated and charged.

The exact checks will depend on the vehicle and failure mode.

Final Takeaway

When a new AC compressor fails soon after installation, the replacement part is not necessarily the only thing to investigate.

Contamination, moisture, incorrect oil, excessive system pressure, incorrect refrigerant charge and problems with other AC components can all affect compressor reliability.

The most important step is to understand why the original compressor failed and whether that problem has been properly addressed.

Choosing a quality replacement compressor is important, but so is making sure the AC system is correctly prepared and the replacement unit is installed according to the appropriate procedure.