How to Recharge Your Car’s AC at Home

Feeling a little hot behind the wheel? If it’s not road rage, it might be a depleted AC system in need of recharging.
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person feeling for car air conditioner temperature with hand in front of vents


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If your car AC isn’t cooling like its usual frosty self—or worse, if your car AC is blowing hot air—the chances are pretty good that your AC system is probably still working. It just needs to be recharged, and a car AC recharge is a fairly easy project, even for beginners. This guide will explain how to recharge your car AC so you and your passengers can stay cool on the road.

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Project Overview

Working Time: 20 minutes
Total Time: 20 minutes
Skill Level: Beginner
Estimated Cost: $30 to $60

Before You Begin

There are a few important things to know before recharging the AC in a car:

  • Modern vehicles use R134a refrigerant while those built before 1993 use R12 refrigerant. Recharging an R12 system is not a DIY job and is best left to an auto AC professional.
  • AC refrigerant can cause frostbite if it touches skin or blindness if it contacts eyes, so wear gloves and eye protection.
  • Ambient temperature during the time of recharging determines how much pressure should be in the system. Refer to the recharge kit’s instructions and your vehicle’s owner’s manual.
  • You will be running your vehicle’s engine while you’re recharging the system, which means there will be spinning belts and pulleys and hot parts that can burn to the touch. Tie back long hair, wear a top with sleeves, pants, and close-toed shoes, and be careful of hazards under the hood and in your workspace.
  • If your AC system is visibly damaged, you can’t use an auto AC recharge kit. It will need to be repaired by a licensed technician.
  • If your system reads “zero” when the gauge is attached, it’s likely too damaged to recharge. It will require professional repair.
  • If you’re unsure how often to recharge car AC systems, the answer is once. If you’re recharging yours several times over a short period of time, there is a leak and it should be repaired by a pro. Refrigerant leaks are environmentally harmful and should be fixed as soon as possible.

We often find our car and truck ACs need maintenance in spring. This is because many leaks occur over the winter, when seals and other AC system parts condense and shrink, allowing refrigerant to escape. You can combat this by using a recharge kit with sealant and conditioner already mixed in.

RELATED: 12 Ways to Stay Cool When Your Car’s AC Gives Out 

homeowner recharging car ac

STEP 1: Locate the low-pressure port and AC compressor.

If your AC isn’t blowing cold air, before starting the vehicle or hooking anything up, locate two important items: the low-pressure port and the AC compressor.

The ports will be the barb-like fittings sticking out from the metal AC conditioning line under the hood. There should be two—the lower pressure port, which is on the thicker pipe, and the high pressure port, which is on the thinner pipe. You want the low-pressure port. Remove the cap and place it aside (ideally somewhere you won’t lose track of it).

Next, look for the AC compressor. This is a pump-like device attached to the front of the motor. It will have a belt that wraps around a pulley, and the refrigerant lines will run to and from it.

With these two items located, you can get started recharging your car’s AC.

STEP 2: Check the ambient temperature and pressure range.

The temperature of the air around your vehicle impacts the ideal pressure in the system. Check the temperature and then reference the pressure chart in your chosen recharge kit’s paperwork or your vehicle owner’s manual to determine the appropriate pressure.

Do not recharge a car AC if the ambient temperature is lower than 55 degrees Fahrenheit, as doing so can damage the system.

STEP 3: Start the car and turn up the AC.

With the hood open, turn the car on and crank the air conditioning down to its coldest and up to its most powerful settings. Leave the car running and look at the AC compressor pulley under the hood. Does it appear that that entire pulley is spinning or is the outermost plate (known as the clutch) stationary? This will answer one of two things:

  1. If it’s spinning, the AC compressor is working properly and the pressure in the system is simply low.
  2. If it’s not spinning, the AC system is extremely low on pressure.

In either case, move on to Step 4.

STEP 4: Shake the can well and attach it to the low-pressure port.

Vigorously shake the can of refrigerant to mix up all of the ingredients inside evenly. Once well-shaken, remove the safety seal (this will differ from product to product) and attach the hose to the low-pressure port, taking care to avoid touching any moving or hot engine parts.

To attach the hose, place the quick-connect nozzle over the tip of the port. Pull back on the snap ring and press the nozzle onto the port completely. Release the snap ring. Give a few light tugs to make sure it’s attached.

can of car ac refrigerant and pressure gauge for charging AC

STEP 5: Recharge the AC system.

Start charging the car AC system by squeezing the trigger or opening the knob on the recharge kit. If the compressor clutch isn’t spinning, empty half the can into the system, shaking the can every 3 to 4 seconds to keep the contents mixed. If the clutch does not engage after emptying half the can into the system, seek professional repairs from a licensed auto care center.

If the clutch is engaged and spinning, continue filling the system. Shake the refrigerant can slightly every 3 to 4 seconds, and check the pressure gauge often. Recharge the system until the pressure gauge reaches the desired PSI for the ambient temperature.

STEP 6: Check the temperature inside the vehicle.

After filling the system to the desired pressure, head back into the vehicle and feel the air coming from the vents. It should start to feel very cold, which should mean that the recharge was successful. If it doesn’t feel any cooler, you may need to take your vehicle to a professional repair shop to have the problem diagnosed and repaired.

RELATED: 12 Maintenance Mistakes That Shorten the Life of Your Car

Final Thoughts

With that, your AC system should be back to its former glory, pumping cold, crisp air to keep you cool on hot days. If successful, this DIY repair can save you hundreds of dollars over taking the car to a repair shop. There are a lot of benefits to being your own mechanic!

However, if you don’t feel your DIY skills are up to the task, or your home repair wasn’t successful, it’s better to pay a pro than to risk hurting yourself or damaging your vehicle’s AC system any further. Most local repair shops can handle basic AC repairs, so it’s best to lean on an expert rather than going far outside of your comfort zone or DIY capabilities.