Four common causes for a vehicle AC not working and their related parts.

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Is The AC In Your Car Not Working?

The air conditioner isn’t working because of a faulty compressor clutch, cracked evaporator core, loose hose, frozen expansion valve, or cracked condenser core.

A car air conditioning system needs an experienced professional who can promptly diagnose and fix the problem. Doing so ensures that proper investigations as to why the AC is blowing hot air or none at all happen by good procedures. Remember, a minor issue can quickly become a bigger headache if unaddressed. So why suffer when you can act now and avoid future troubles?

Watch out: A car AC not working requires quick attention. Neglecting your car's air conditioning issues can put your safety at risk — think of molds, hot days, no comfort, etc. — and leave you with a hefty repair bill, since issues can progress silently.

The most common causes for a vehicle’s AC not working

The most common causes for the car’s AC not working:

Faulty compressor clutch: The compressor clutch is an electrical "lever" that controls when the compressor inside the air conditioning turns on and off. The compressor is needed to make your air conditioning work and cool down; it's a component that circulates coolant inside the AC system. Therefore, if the clutch fails, the compressor might not engage, causing AC problems.
Leaking evaporator core: The evaporator core is a component inside the AC system, sitting behind the dashboard, that is extremely cold, cooling the air passing by it and releasing it into the cabin. So, it's vital to make cold air leave the vents. However, if the evaporator core fails, it might stop cooling down, resulting in bad AC efficiency.
Leaking condenser core: The condenser core sits in front of the radiator, it uses pressure to turn refrigerant from gas to liquid. This liquid then becomes vital for the cooling cycle. However, if the condenser is faulty, the cooling cycle loses efficiency, resulting in AC issues.
Leaking air conditioning hose: Air conditioning hoses are rubber tubes transporting coolant from the cooling system into the AC. If these hoses get cracks, gaps, or lose sealing, they'll allow coolant to leak out, resulting in AC issues.
Expansion valve freeze: The expansion valve manages the refrigerant amount flowing into the evaporator core. However, since this valve is in the eye of the storm, it can sometimes freeze and lose its capacity. In this case, coolant might leak out due to overflowing.
Faulty compressor: The compressor pressurizes and circulates coolant inside the AC system, much like a pump. If the compressor is faulty, coolant might not effectively flow inside the system, resulting in bad cooling performance and AC issues.

Frequently Asked Questions

Do you hear an unusual sound from the hood when you turn the AC?

The compressor clutch is a part of your car's air conditioning system that helps turn the AC on and off, depending on when it's needed. It uses electricity from the battery to activate an electromagnetic mechanism that engages or disengages the compressor. When the clutch works properly, it quickly engages the compressor when the AC is active, making it turn smoothly and quietly. However, if the electricity going to the clutch is weak, the clutch might slip and make an unpleasant noise. Over time, the clutch can wear out, which can also cause noise. This is because the clutch plate has little flexible parts called tangs that move every time the clutch is activated. Eventually, these tangs can break, which causes a strange noise when the clutch tries to engage.
Do the vents release a strange sweet smell?

The evaporator core is a part of the air conditioning system in your car that is located under the dashboard inside an air box. As time passes, the oil in the air conditioning system can become acidic and damage the inside of the evaporator, which can lead to leaks. Additionally, vibrations from the vehicle can also contribute to this issue. When the evaporator leaks, refrigerant oil leaks out and gets mixed with the air, causing a noticeable smell from the vents.
Do you see green oil dripping underneath your front bumper?

The condenser is a component of your car's air conditioning system in front of the radiator. Its job is to release heat inside the vehicle to the outside air. Since the condenser is located at the front of the car, it is often the first part to get hit by any debris that bounces up from the road. If the condenser gets damaged, it can cause the refrigerant oil and freon to leak out. You can quickly spot the green refrigerant oil underneath the front bumper.
Is your AC compressor activating and deactivating rapidly?

Air conditioning systems use hoses of metal ends attached to hoses with a rubber exterior and a plastic interior lining. These hoses can develop leaks from rubbing and shaking against other parts. When these hoses leak, they release a gas called freon. As freon in the system leaks, the pressure on the low side drops, causing the compressor to turn on and off quickly. This rapid turning on and off is called short cycling.
Does your AC start to cool nicely, then shut down suddenly?

A leak in the air conditioning system can cause water to enter it. When the freon passes through the expansion valve, there is a rapid drop in pressure and temperature. If there is any water in the freon, it can freeze at the orifice of the expansion valve and block it. This can cause the air coming out of the air vents in the vehicle to become very cold until the orifice is completely blocked with ice. As a result of the blockage, the compressor shuts off due to the high-pressure safety switch being triggered by accumulated pressure. When this happens, the temperature in the vehicle rises to the outside temperature. It takes significant time for the expansion valve to thaw and for the AC system to start working again.
Is your air conditioning compressor getting louder over time?

The air conditioning compressor compresses the freon, which is in a vapor state after passing through the expansion valve in the evaporator. By compressing the freon, the pressure increases, allowing the condenser to turn it back into a liquid. To keep the compressor working smoothly, refrigerant oil is mixed with the freon to lubricate any moving parts. However, if there is a leak in the system and the freon level drops, the compressor may not receive enough oil. As a result, the moving parts wear out, and the compressor makes a noise.

Typical fixes to address the cause(s)

These are typical processes and repair services that fix a check engine light issue

The most common cause: Faulty compressor

The most common reason for a car’s AC to stop working is a faulty compressor. The compressor is a sort of pump that pressurizes coolant and ensures it runs and flow nicely inside the AC system. The AC compressor is an electrical component and relies on a clutch to engage/disengage. So, problems affecting the vehicle's electrical system directly result in compressor issues, leading to AC malfunction.

Symptoms it causes: Apart from the AC not working, you might notice squealing noises, humming noises, hot air from the vents, etc.
Medium risk of priority: The compressor is essential for your vehicle's AC system to work. Without a working compressor, electrical components surrounding the air conditioning system can overstress or develop further damage, resulting in heftier repairs.

How exactly does the compressor go faulty?

The compressor relies on connectors, clutches, fuses, and anything electrical-related. It can develop internal wiring issues due to wear and aging, it can suffer short-circuit, or it can get bad connectivity due to cables loosening up. The compressor typically lasts for many years, but it can eventually go bad and start acting up. An issue with the vehicle's electrical system can also indirectly overstress the compressor, damaging it.

Go safe: Ask for a mechanic to inspect your vehicle’s AC system to investigate if the compressor is faulty due to surrounding components and if there’s further damage to check out. Many shops do transparent vehicle inspections and lay out your options after investigating your vehicle’s conditions.

What’s a vehicle inspection? It’s “detective work” on your vehicle, checking its systems to see if anything prevents the car from working as expected. In this case, mechanics examine different parts of your vehicle to track if anything is causing the compressor to wear out. They’ll also check the condition of components during their inspection, noting which are causing the problem and which got affected by it, recommending to replace them in order of priority.

Transparency example in a faulty compressor service

An AC system inspection is the most transparent process to understand why your vehicle’s compressor is faulty. This is because many components surrounding the compressor, evaporator, and blower motor can have a say in the issue, indicating the real culprits that caused it all.

Let’s read an example of how this kind of inspection helps to service a faulty compressor.

A customer brought their vehicle to the shop concerned about a loud noise from under the engine. They weren't sure what was causing it, but they noticed the noise disappeared when the air conditioning compressor cycled off.

During a test drive, the technician noticed the compressor was very loud. Upon a vehicle health inspection, the technician found that the air conditioning compressor had oil leaking out of the case half.

To diagnose the problem, the technician recovered the freon and removed the discharge hose from the back of the compressor. The technician found small metal parts inside the discharge port that had turned the surface silver. Additionally, the orifice tube was clogged with metal particles, confirming the debris was coming from the compressor.

Based on the amount of debris and damage to the compressor, the technician recommended replacing the compressor, condenser, accumulator, and orifice tube. They also recommended flushing the hoses and evaporator with AC front flushing solvent.

Once these components were replaced and the system was flushed, the technician added the manufacturer-recommended amount of refrigerant oil. Finally, they recharged the system with freon to the manufacturer's specifications.

Faulty compressor

In this case, the mechanic put the “Immediate Action” tag on the compressor.

Similar Symptoms

Below are just a few examples of typical Symptoms and Fixes your car might be experiencing

Four common causes for an AC not cooling the vehicle and their related parts.

Is The AC In Your Car Not Working?

The most common causes for a vehicle’s AC not working

Frequently Asked Questions

Do you hear an unusual sound from the hood when you turn the AC?

Do the vents release a strange sweet smell?

Do you see green oil dripping underneath your front bumper?

Is your AC compressor activating and deactivating rapidly?

Does your AC start to cool nicely, then shut down suddenly?

Is your air conditioning compressor getting louder over time?

Typical fixes to address the cause(s)

The most common cause: Faulty compressor

How exactly does the compressor go faulty?

Transparency example in a faulty compressor service

Similar Symptoms

Why Is My Car's AC Not Blowing Cold Air?

Why Is My Car's AC Blowing Hot Air?

Why Is My Car Overheating When I Turn The AC On?

Why Does My Car's AC Sometimes Work And Sometimes Don't?

Why Does My Car AC Smell Like Vinegar?