Hey, Why Is My Car's AC Not Working?

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Four common causes for a vehicle AC not working and their related parts.
The air conditioning system in your vehicle is a closed system. Under normal circumstances, the system will maintain the pressure inside and operate continuously. Adverse conditions under which the vehicle's air conditioning system operates are extreme heat, excessive vibration, and other environmental hazards. When any of the components in the AC system develop a leak, the freon will escape into the atmosphere, and the air conditioning system will not work.

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 AC not working requires quick attention. Neglecting your car's air conditioning issues can put your safety at risk and leave you with a hefty repair bill.

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?

Let's Get To The Bottom Of It!

  • Q: 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.

  • Q: 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.

  • Q: 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.

  • Q: 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.

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Vehicle Health Inspection Proof

Explore the following typical inspection results that show a potential cause for the symptom and select the one you believe is similar to your vehicle's issue.

Faulty compressor clutch

The proof image shows a failing AC clutch that makes noise when engaged.

A customer brought their vehicle complaining that their air conditioning stopped working a few days earlier. They suspected the compressor was the problem, as they heard an unusual noise when trying to turn on the AC.

During the test drive, the technician verified that the AC was not functioning and that the noise was present when attempting to engage the compressor. Furthermore, the noise remained even when the compressor was disengaged and gradually faded.

During the vehicle health inspection, the technician noticed the compressor clutch was broken. To investigate further, the technician tested whether the battery voltage was getting to the compressor clutch when the AC was turned on. They found battery voltage at the compressor clutch coil when the AC was activated.

To assess the system's condition, the technician then evacuated the freon from the system, checking for any debris or other issues. Then, they readded the substance considering the recommended for the vehicle's capacity.

Next, the technician took the high-pressure line off the compressor to check for any debris in the compressor line. However, they found no debris in the discharge line.

Based on their observations, the technician recommended replacing the compressor clutch assembly and recharging the system. This will restore the functionality of the air conditioning and fix the issue of the broken compressor clutch.

Does the issue look like this? if not accessible your shop will document it
Leaking evaporator core

The image shows the UV dye that pinpointed the leak's location from the evaporator core after removing it from the air box.

A customer dropped off their vehicle, mentioning a strange smell from the air conditioning vents; they also complained it was weaker.

Upon further inspection during a test drive, the technician noticed a distinct smell of refrigerant oil from the vents. However, they didn't see anything more about the customer's concerns.

During the vehicle health inspection, the technician discovered that the cabin air filter was clean, so it wasn't a clogging problem. Nevertheless, the customer authorized additional tests to resolve the issue.

The technician then checked the Schrader valves to verify the UV dye in the system. They found UV dye, so the technician investigated the hoses, compressor, and condenser for leaks with a UV light. However, no leaks were detected.

The technician then used an electronic detection device to sniff around the air box and the airbox drain, which led them to detect an indication of a leak coming from the evaporator. They gained access to the evaporator and verified that the evaporator core was indeed leaking with the UV light. This was causing the strange smell and the decrease in air conditioning performance.

The technician recommended replacing the evaporator core to fix the problem and restore the air conditioning system to proper working condition.

Does the issue look like this? if not accessible your shop will document it
Leaking condenser core

The proof image shows the leak's location in the condenser, causing AC oil to leak onto the ground under the bumper.

A customer dropped off their vehicle, complaining that their air conditioning wasn't performing as well as usual. They also suspected a possible coolant leak due to green fluid underneath the bumper.

During the technician's test drive, they noted that the air conditioner wasn't cooling well. After conducting a vehicle health inspection, the technician found that the condenser had a lot of oil residue on the bottom of the core, and the coolant was at the full mark. However, no other conditions regarding the customer's concern were noted.

The condenser is a component in the air conditioning system that removes heat from the refrigerant, allowing it to return to a liquid state. When the condenser is damaged or leaking, it can cause the refrigerant to leak out of the system and prevent the air conditioning from working correctly.

The technician then requested additional tests, and with authorization, they used a UV light and found that the leak was coming from the condenser, not the hose. The technician recommended a freon recovery, adding 2 oz of refrigerant oil, replacing the condenser, evacuating, and recharging the AC system.

In this case, the oil residue on the condenser core indicated a leak, and the green fluid underneath the bumper was likely coolant mixed with the refrigerant. If left untreated, the air conditioning system would fail, and the leak could cause other vehicle problems.

To prevent this, the technician recommended replacing the condenser and adding refrigerant oil to ensure the air conditioning system was adequately lubricated. They also evacuated and recharged the system to ensure it was functioning correctly.

Does the issue look like this? if not accessible your shop will document it
Leaking air conditioning hose

The technician's proof image shows the UV dye glowing at the location where the hose is leaking. This dye helps to precisely locate the leak, which is tough to spot without specialized equipment.

A customer brought their vehicle in for service, concerned about their faulty air conditioner. They mentioned hearing the compressor going on and off quickly, and the air conditioning was not cooling as usual.

During the test drive, the technician confirmed that the air conditioning was not working well. However, the technician found nothing related to the customer's concerns during the vehicle health inspection. So, the customer authorized an additional diagnostic check.

The technician checked the Schrader valves to see any UV dye in the system, but they could not find any evidence of dye. Then, the technician hooked up the AC machine, started the vehicle, and turned on the air conditioning. The low side pressure dropped below 30 PSI, and the compressor was short cycling.

To summarize, Schrader valves are a type of valve commonly used in pneumatic and hydraulic systems to control the flow of fluids or gases.

The technician recovered the freon and evacuated the system to fix the issue. They then injected 2 oz of UV dye and oil and recharged the system. Next, the technician ran the air conditioning for 20 minutes before using a UV light to check for leaks.

Finally, the technician found that the pressure hose from the compressor was leaking at the crimp. As a result, the high-pressure line will need to be replaced.

Does the issue look like this? if not accessible your shop will document it
Expansion valve freeze

The proof image shows the frost accumulating outside the expansion valve, causing the AC to malfunction. This issue was due to moisture in the freon, causing the orifice in the expansion valve to freeze.

A customer dropped off their car reporting that the air conditioning system was malfunctioning; it would sometimes shut off randomly and only restart after the vehicle sat for a while. They also mentioned that the AC worked well for the first 20 minutes after starting the car but would stop working after about 30 minutes.

The technician took the car for a test drive and confirmed that the AC would stop working after about 30 minutes, validating the customer's complaint. During a vehicle health inspection, the technician did not notice any issues related to the customer's complaint. Then, the customer authorized additional tests.

The technician hooked the car to an AC machine and ran the air conditioner. After about 15 minutes, the technician observed that the "high" side pressure increased while the "low" side decreased until sucking like a vacuum. Finally, the high side reached 400 PSI, causing the compressor to shut off.

In this context, an AC machine is specialized equipment for diagnosing and servicing vehicle air conditioning systems.

The technician noticed that the expansion valve was covered in frost, indicating that the moisture in the freon froze up the orifice in the expansion valve. The technician warmed up the expansion valve with a heat gun and found that the compressor would only stay on for about 5 minutes before the expansion valve froze again.

The technician then recovered the freon and found it was marginally low. So, they evacuated the system for 30 minutes to ensure it was dry and recharged it to the specified freon amount.

Does the issue look like this? if not accessible your shop will document it
Faulty compressor

The proof image shows the failing compressor that has continued to get louder when running and is starting to leak, affecting the whole electrical system.

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.

Does the issue look like this? if not accessible your shop will document it

Typical Fixes to Address the Cause(s)

The following chapters bases themselves on experiences from our auto repair shop; we'll describe related problems' causes and fixes.

"Compressor clutch replacement" fixes "Faulty compressor clutch"

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Hey, Why Is My Car's AC Not Working?
Sometimes a problem is more challenging to describe than it initially looked like. If you are not sure your problem is described by this article, please find below similar vehicle symptoms, which might describe better the issue you are experiencing.

Other things your auto repair shop might talk about:

AC not working in car. cool air. cold air. warm air. blowing cold air. Blowing warm air. Refrigerant leak. AC evaporator. Low refrigerant. blown fuse. stay cool. blower motor. c system.