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Blog - Car AC Not Blowing Cold

August 13, 2020

5 Tricks to Try When Your Cars A/C Is Not Blowing Cold Air

The last thing you want while driving in the summer is a broken A/C system. But air conditioning systems are complicated — and there are a number of reasons why you may find your car's A/C blowing hot air instead of a cool, refreshing breeze. For help with your cars A/C troubleshooting, here are a few things to check to help keep you comfortable all summer long.

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How Car A/C Works

Before pinpointing any one problem with your car's A/C, it helps to have a general understanding of how the system works. It all comes down to thermodynamics and the pressure-temperature relationship of the refrigerant running through your A/C system.

Your car's A/C is a closed system that cycles refrigerant between states of high and low pressure. When the refrigerant undergoes a pressure change, it gives off heat energy, which is measured in temperature. That means when refrigerant from the high-pressure side loses pressure, it rapidly drops in temperature. Similarly, when low-pressure refrigerant is repressurized again, its temperature increases. This constant conversion of high- to low-pressure refrigerant creates the cooling effect on the air that gets blown into your car's cabin.

There are five major components to your car's A/C system that enable this pressure-temperature exchange:

• Compressor: Pumps refrigerant throughout the system and repressurizes low-pressure gas refrigerant into hot, high-pressure gas.
• Condenser: Located in front of your car's radiator. Precipitates high- pressure gas refrigerant into liquid form. Transfers heat outside the vehicle.
• Receiver/Drier or Accumulator: Removes moisture and contaminants from liquid refrigerant. Depending on your vehicle, you may have a receiver/drier or accumulator.
• Expansion Valve or Orifice Tube: Regulates pressure and temperature changes in A/C system by controlling how much liquid refrigerant is depressurized into gas. Depending on your vehicle, you may have an expansion valve or an orifice tube.
• Evaporator: Located inside the dashboard of your Nissan. Removes moisture from air and provides a source of cold air that pours through passenger cabin vents.

Here's how all of these components work together: When you turn on the A/C in your car, you activate the compressor which starts pumping refrigerant throughout the system and turns the refrigerant inside it into a high-pressure gas. This hot, high-pressure refrigerant then moves from the compressor to the condenser. The condenser turns the high-pressure gas into liquid form, causing it to lower slightly in pressure and temperature.

From the condenser, the high-pressure liquid refrigerant passes through the receiver/drier. The receiver/drier traps any contaminants and moisture in the liquid refrigerant before it reaches the expansion valve or receiver tube. Depending on your A/C settings, the expansion valve will let more or less refrigerant through.

In the process of passing through the expansion valve, the refrigerant loses pressure, cools off, and expands into a gas. This low pressure gas then enters the evaporator where it absorbs the heat from inside the passenger cabin. As the refrigerant absorbs heat, the evaporator drops to frigid temperatures.

Once cold, a fan — called the blower motor — blows air over the chilled evaporator and into the passenger cabin, providing you with cool, refreshing A/C. Finally, the low pressure refrigerant gas exits the evaporator and enters the compressor where the cycle starts all over again.

Troubleshooting Your Car's A/C

When it's all working properly, your A/C system provides wonderful relief from the summer heat. But if even one part of the system fails, you could end up with a face full of hot air. Plus, with so many components in this complicated system, there are a number of ways your A/C could malfunction.

1. Replenish Low Refrigerant

Low refrigerant is one of the most common causes of A/C blowing hot. Even though your A/C system is supposed to be a "closed system" — meaning the pressure inside the system isn't affected by outside atmospheric pressure — it may lose effectiveness over time. Excess heat, vibrations, and general wear and tear can lead to small leaks that are hard to detect.

Sometimes the solution is to simply replenish the amount of refrigerant in your system. However, if you find that you are having to recharge refrigerant often, you likely have a leak or failed component — oftentimes the condenser or compressor — that's causing you to lose refrigerant.

Check the components and A/C lines for visible leaks of a green, oily substance, or use a UV-light detection kit to spot small, hard-to-find leaks. For a best-practices method, have a Nissan Certified Technician examine your A/C system for any issues.

2. Check For Compressor Failure

Without a working compressor, the refrigerant cannot be pressurized or pumped through the system. There are a number of things that could be causing your compressor to malfunction, including a failed A/C clutch or cycling switch, a blown fuse, contamination from worn parts inside the compressor, or low refrigerant caused by leaks.

With the engine on and A/C set to max, check if the clutch is engaging with the compressor. A functioning clutch will be steadily rotating and making a clicking sound. If the clutch is engaged, use a voltmeter to check for any voltage reaching the compressor. If there is no voltage, you may be dealing with a blown fuse or faulty cycling switch.

3. Consider Condenser Failure

When the condenser malfunctions, you may experience hot air blowing through the vents, or worse — your engine could overheat! Since the condenser sits near the engine and is the primary heat exchanger in the A/C system, it must be constantly cooled to prevent overheating inside the cabin and under the hood.

You may experience condenser failure if contaminants from the compressor or receiver/drier enter the condenser and restrict the flow of refrigerant, leading to ineffective cooling. Other causes may be an inoperable condenser cooling fan or leaks in the system.

4. Clean Clogged A/C Lines

When the flow of refrigerant is restricted in one area, the whole A/C system is affected. Your A/C lines and components like the compressor and evaporator may be clogged with contaminants that damage parts or limit the flow of refrigerant throughout the system.

Contamination often occurs from a failure within the receiver/drier. Desiccants, a material that removes moisture, may leave the receiver/drier and cause major damage to the compressor and other A/C components. Contamination may also occur from particles of worn parts that become dislodged and flow out of place.

5. Check Evaporator Drain

When experiencing A/C problems, your evaporator may be failing due to a leak in the evaporator core. Typically, this is the result of wear and tear over the lifetime of your evaporator. Without the evaporator to absorb cabin heat and provide cool, crisp A/C, you'll be sweating in your seat.

Check the evaporator drain tube beneath your car for any green, oily refrigerant leakage. Use an electronic leak detector if a larger leak is not visible.

Beat the Heat with Ice Cold A/C

Does your Nissans A/C need repairs? Find genuine Nissan car A/C parts like compressors and filters made to fit your make and model — or schedule an appointment with our certified Nissan technicians to have your A/C serviced. We recommend seeing our Certified Nissan technicians for this service.

Material in this article is for general information purposes only and was accurate as of the date of first publication. Information is subject to change and does not constitute an offer, representation or warranty (express or implied) by Nissan North America, Inc. ("Company"). Interested parties should confirm the accuracy of any information in this website as it relates to a vehicle directly with Company before relying on it to make a purchase decision. Unless expressly referenced, Company does not endorse and is not affiliated with any company that might be mentioned in this article. Company is not responsible or liable for the availability of links to websites or resources, or for any content, advertising, products, services, privacy policies, or other materials on or available through these websites or resources, or for your reliance thereon. Any references to data or products are subject to change without notice. Trademarks are property of their respective owners.

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