7 Signs of a Faulty AC Compressor

The main sign of a faulty AC compressor is a lack of cold air coming from the AC. In many cases, the air conditioner can actually blow warm air instead. This happens because the AC compressor is vital in pressurizing refrigerant fluid, so it's the key component in absorbing heat from inside the cabin to lower temperatures.

The AC compressor "compresses" the refrigerant fluid, which causes a physics reaction, making the fluid absorb heat; the heat it absorbs comes from inside the vehicle. Note that the fluid becomes gas once it gets in the compressor. The compressor then releases the hot gas outdoors.

This translates to: AC compressors make your air conditioner blow cold air.

• Key function: The main function of an AC compressor is to ensure the AC is working. Therefore, it's vital to provide comfort inside the vehicle cabin.

A faulty AC compressor can not only cause the AC to stop working properly but also make room for progressive damage to different internal components.

• Safety: A faulty AC compressor might cause different safety-risky situations. For instance, the vehicle's defrost function might not work if the AC compressor is faulty, making the driver unable to defrost the windshield if visibility is bad. A faulty AC compressor can also damage progressively and lead to electrical issues, making the vehicle unpredictable.

AC blowing warm air

When the AC compressor goes bad, the vehicle's air conditioning system malfunctions noticeably. One of the most noticeable problems is the AC vents blowing warm air instead of cold air.

The compressor is responsible for absorbing the heat inside the cabin and converting warm air into cold air. However, when the compressor is faulty, the air's heat isn't absorbed; it simply circulates and returns warm inside the vehicle cabin.

Additionally, if the compressor damages other AC components like wires or the AC evaporator, causing electrical overheat, the air might come out even warmer from the vents.

Burning rubber smell

A problem with the AC compressor is never a good sign. The compressor might have internally shorted or malfunctioned due to something else. Either way, there's a high chance the problem is electrical.

Electrical issues inside the air conditioning system commonly result in overheating and further damage to other components. Therefore, extra heat inside the air conditioner can burn or melt wires, insulations, rubbery components, etc., this commonly results in a burning rubber smell inside the vehicle.

Other signs

• Grinding Noises
• Leaking Refrigerant
• Compressor Clutch Not Engaging
• Inconsistent Cooling
• Foggy Windshield

Possible fixes

• AC control unit replacement: If the AC compressor fails, it can disrupt the regulation of the refrigerant, causing the AC control unit to malfunction and require replacement.
• HVAC control replacement: A failing AC compressor can result in poor refrigerant circulation, leading to the HVAC control system’s inability to maintain the desired temperature, which may necessitate a replacement.
• AC compressor replacement: A malfunctioning AC compressor can overheat and seize if it can't circulate refrigerant properly, resulting in the need for its replacement.
• AC condenser replacement: When the AC compressor fails, it can cause the refrigerant to not flow correctly, leading to the AC condenser overheating and becoming damaged, thus requiring replacement.
• AC control module replacement: A faulty AC compressor can lead to inaccurate refrigerant regulation, causing the AC control module to malfunction and need replacement.
• AC pressure switch replacement: If the AC compressor is not functioning properly, it can cause incorrect pressure readings in the system, leading to the AC pressure switch failing and needing replacement.
• AC hose replacement: A damaged AC compressor can create excessive pressure or cause refrigerant leaks, which may damage the AC hoses and require replacement to ensure the system can hold refrigerant properly.

Frequently Asked Questions

Is it OK to drive with a bad AC compressor?

While it's technically possible to drive with a faulty compressor, it's not recommended. It can strain your engine, damage your air conditioning unit, reduce airflow, and lead to leaks or damage to other parts of your AC system. If you hear strange noises, get lukewarm air, or notice other signs of a failing compressor, address it soon to avoid further issues.

How do I test my car's AC compressor?

Testing a car's air conditioning compressor involves checking various components. You can start by listening to strange noises from the engine bay with the AC on. A multimeter can help measure the voltage at the compressor clutch and check for electrical faults. Some advanced checks involve refrigerant pressure gauges, but for those, it's best to consult a mechanic.

Can you fix the AC compressor without replacing it?

In most cases, fixing an AC compressor without replacing it is not recommended for DIYers. The compressor is in a sealed AC unit, and refrigerant handling requires specific tools and certifications.  However, mechanics can sometimes replace the compressor clutch or electrical components if those are the failing parts.