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How to Recharge Your Car’s AC System

Air Conditioning Controls

It’s time to recharge your car’s AC when you start to notice that the air blowing out of your dash vents isn’t quite as cool as it was just a few weeks before. There are several possible reasons as to why your air conditioning system might not be functioning correctly. Fortunately, it’s relatively easy to get it charged up with refrigerant and get back to battling the summer heat.

Why Do You Need to Recharge Your Car’s AC?Car air conditioning

If your automobile’s air conditioning is blowing warm, or simply not cold air, it’s almost always because there’s a leak somewhere in the system. The leak causes the level of the unit’s refrigerant — which for most modern cars is known by the technical terms R-134a and R-1234yf — to get lower and lower. If the leak is slow enough, it can be difficult to detect, and sometimes your car’s AC compressor will shut down automatically once the refrigerant volume has dipped to a certain point, to protect it from damage. If it’s a major leak, and the refrigerant leaves all at once, then you might notice that the compressor isn’t even clicking on when you activate the system.

How Do You Fix Your Car’s AC?

Once you decide to recharge your car’s AC, ideally you should head to a professional garage that has the required equipment and training to deal with air conditioning systems. Refrigerant is harmful to the environment if it’s released freely into the atmosphere, which is illegal to do in almost every municipality. The refrigerant must be captured in a special machine to be recycled. Also an empty AC system can be damaged by humidity from outside air. The longer an AC system is open to the atmosphere, the more likely that water finds its way into the wrong places. Trained technicians will attach a device to your car’s air conditioner that will inject a fluorescent dye that will track any leaks as the colored gas leaves the system. Once the leak is located the technician can assess which parts need to be replaced and do the work quickly. The repair process involves hooking up a special high-powered vacuum pump to remove all air from the system while monitoring the system for any leaks. The vacuum also helps remove any trapped moisture from the closed-loop system. When the leak has been repaired, your mechanics can then flush and fill your car with the proper refrigerant.

Self-Refills Offer A Quick Solution

What if you don’t have time to go see a mechanic or just need a little more time to plan a proper repair? You can always recharge your car’s AC yourself using a self-recharge kit. Some kits offer a cylinder filled with a mixture of refrigerant and sealants that are designed to stop any leaks that your car might have. The biggest issue with using this type of solution is that, over time, the sealants may cause problems inside the AC system — and if there’s a major physical leak, you’re just wasting your cash as the refrigerant will continue to escape.

Here’s how to recharge your AC system using a self-refill kit. This is a generic instruction list and may vary by vehicle and chosen self-refill kit:

  1. Read all of the instructions included with the self-refill kit, as some products may vary. Take note of the included temperature / pressure chart you will need to reference later.
  2. Safety first. Put on a pair of safety glasses and work gloves.
  3. Open hood of the vehicle.
  4. Locate the low side AC system service port. It will be located on the line that runs between the AC compressor and the condenser. The low side service port is a different size than the high side service port to help prevent accidently using the wrong one.
  5. Once you have located the low side AC system service port, start the engine. Set the AC system to maximum cooling and maximum fan speed.
  6. Before touching the self-refill kit, observe the AC compressor for functionality. The AC compressor clutch should engage (allowing the center of the AC compressor pulley to spin) and disengage. If the AC compressor clutch does not engage while the AC system is turned on, then the refrigerant level may be low.
  7. Remove the protective cap from the low side service port and attach the self-refill kit hose. Gently tug the self-refill kit hose connector to verify it is firmly connected to the low side service port.
  8. Following the instruction included with your specific self-refill kit, check the refrigerant level. Remember that refrigerant level is not like a fuel gauge, the fill level pressure is also based on outside air temperature and can vary. Refer to the the self-refill kit temperature / pressure chart.
  9. If the system is low enough that the AC compressor does not engage, follow the instruction included with your specific self-refill kit and add refrigerant slowly. At this point the AC compressor should start cycling on and off. (Note: if the AC compressor fails to engage after adding refrigerant, we highly recommend visiting your local NAPA AutoCare for a thorough diagnosis and repair.)
  10. With the AC compressor cycling you can now measure the system pressure. When the AC compressor clutch is engaged, read the self-refill kit pressure gauge and compare it with the temperature / pressure chart. Only read the gauge when the AC compressor clutch is engaged as it will not be accurate otherwise.
  11. Slowly add refrigerant until the self-refill kit pressure gauge reads the correct pressure according to the temperature / pressure chart. There may also be a green zone on the gauge to help identify when you are getting close.
  12. Once the correct pressure has been reached, disconnect the self-refill kit hose from the low side service port. Do not add any more refrigerant than necessary, as too much refrigerant can cause damage to the AC system.
  13. Place the protective cap back on the low side service port and close the hood.
  14. Enjoy the cool air!

Self-recharge kits can work, but they are not always a long-term solution. In general, it’s always best to go see your local NAPA AutoCare expert when your car’s system needs to be recharged.

Check out all the air conditioning system parts available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information about your car’s AC system, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of Freeimages.

Benjamin Hunting View All

Having been bitten by the car bug at a young age, I spent my formative years surrounded by Studebakers at car shows across Quebec and the northeastern United States. Over ten years of racing, restoring, and obsessing over automobiles lead me to balance science writing and automotive journalism full time.  I currently contribute as an editor to several online and print automotive publications, and I also write and consult for the pharmaceutical and medical device industry.

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