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How To Recharge The AC In Your Car: A Step-By-Step Guide + FAQs

July 31, 2022

Ever turned on your AC on a sweltering day, only to get a blast of hot air

This implies your air conditioning system is losing power, and it’s time to recharge the AC! If you don’t soon, the car’s indoor air quality will drop too — thanks to rolled-down windows.

So, how do you recharge the AC? 
Do you need a recharge kit? How do you use one? 

Don’t worry. We’ll answer everything!

In this article, we’ll show you how to recharge your car’s AC and solve that warm air problem. We’ll answer some AC-related questions too. 

This Article Contains:

Let’s begin! 

How To Recharge The AC: 11 Easy Steps

Recharging the AC isn’t as simple as replicating an AC recharge service done by a mechanic. So here’s a step-by-step guide on how to use the AC recharge kit.

Note: You can only use an AC recharge kit if your car uses R134a refrigerant.

Also, if you’re unfamiliar with AC repair or car parts, it’s best to let a professional mechanic recharge the AC.

Step 1: Gather The Right Equipment And Materials

Note: Always wear safety glasses when working under the hood. The glasses and gloves will be handy to protect you from the refrigerant, which can dangerous. It freezes quickly on the skin, causing pain. Also, carefully review all instructions and warnings included with your AC recharge kit.

Step 2: Turn On Your AC 

Now that you have all you need, start your car and crank the AC (indoor cooling system) to max or high.

Step 3: Determine If The AC Compressor Is Engaging

An AC compressor (driven by the accessory belt) converts the refrigerant from liquid to gas. When the car air conditioner is on high, the clutch at the end of the compressor should be spinning with the accessory belt. 

If the compressor clutch is engaging, then the system may just have low refrigerant — especially if the AC is still blowing slightly cold air. You should still test the pressure before adding refrigerant. 

If the compressor clutch isn’t engaging the compressor, then:

Adding more refrigerant after testing the pressure will let you know which of these is the cause.

Step 4: Test The Pressure

Next, turn off your car and spot the low-side pressure port (or low pressure port) to test the pressure. The low-side pressure service port is normally on the passenger side of the engine bay. 

You’ll see a black or gray cap on it with the letter “L.” 

Can’t find it?
Check your car service manual to confirm the location of the low-side service port.

Step 5: Wipe Away Dust

Get a clean rag and wipe away any dust. Then remove the cap from the low pressure port.

Step 6: Attach The Recharge Hose

Attach the recharge hose of the recharge kit by placing the quick-connect fitting on the port. Then push down until you hear it click into place. 

Warning: Don’t pull the trigger at this time, or it’ll release AC refrigerant from the AC system into the atmosphere. This will drop the refrigerant level further. 

Step 7: Restart Your Car And Monitor The Gauge

Turn on your car and crank the air conditioner to the highest settings. Then check the gauge by watching the air conditioner compressor engage the clutch. 

Is the compressor engaged and the low side pressure under 40 PSI (pound per square inch)?
Then your AC system is undercharged. You need the reading to be close to 40 PSI.

Note: Over-charging the AC system will cause permanent damage. Ask for professional air conditioning repair if you’re unsure about the pressure and recharging.

Step 8: Thread The AC Refrigerant Can Onto The Recharge Hose

Install the can onto the hose to slowly top off the air conditioning system with liquid refrigerant.

Once the can is threaded, hold the can upright and squeeze the trigger for 5-10 seconds to add the refrigerant to the AC system. 

When you release the trigger, check the pressure gauge to avoid overcharging the system. Continue squeezing the trigger for 5-10 seconds and inspecting the pressure until you’re as close to 40 PSI as possible.

Step 9: Detach The Charging Hose

After recharging your air conditioning unit to the proper pressure, detach the charging hose from the low-side service port. 

Keep the can attached to the charge hose and store it away if there’s additional refrigerant left, in it in a dry, cool spot.

Step 10: Inspect The Service Port Cap Seal Before Reinstalling

Now check for cracks, nicks, or tears on the seal beneath the cap. This seal can act as extra protection if the Schrader valve ever forms a leak.

Step 11: Go Into The Car And Check The Temperature

Take a thermometer and insert it into one of your car AC vents on the driver’s side, next to the steering wheel. Then note the temperature. 

A properly recharged AC system should blow air as cold as 38°F to 45°F (3°C to 7°C). This’ll differ depending on ambient temperature and whether the car has been idle.

Note: If the pressure is more than 40 PSI, it’s considered “high” low side pressure, which can be caused by overcharging or a malfunctioning compressor. In such a case, you should contact a professional mechanic for an air conditioning service.

With that said, you have successfully recharged the car air conditioner. 

Enjoy the cold air from the air conditioning unit vents. You’ll also have better indoor air quality!

Now, let’s check out some FAQs.

4 FAQs About Your Car AC

Here are the answers to some FAQs regarding your air conditioning system. 

1. How Often Do I Need An Air Conditioning Recharge?

It’s best to recharge your car’s AC unit every 1-2 years. 

However, some cars’ air conditioning systems can last 5 years before needing an AC recharge or even an AC repair.

Never miss regular auto service to determine if you need an AC recharge and keep your compressor in good shape. Even the best-made cars lose roughly 10% of the AC refrigerant from their air conditioner systems annually.

2. How To Tell If It’s Time To Recharge The AC?

Here are some indicators that an air conditioning recharge is needed:

3. How Much Does It Cost To Recharge The AC?

A professional AC recharge can cost approximately $150-$300, depending on the make and model of your car. 

The AC recharge cost is usually not very high, especially considering that this air conditioning service also extends the life of your compressor.

4. What’s The Difference Between Coolant And Refrigerant?

The job of a coolant is to heat a car’s interior and cool the engine. 

On the other hand, refrigerant is a part of the AC or indoor cooling system, responsible for cooling the car’s interior.

Final Thoughts

If your air conditioner isn’t blowing cool air, your AC likely has low refrigerant levels, which can happen over time or due to a leak.

You can recharge the AC yourself with a recharge kit and some refrigerant if your car uses R134a refrigerant. However, overcharging is always a risk, and handling the refrigerant must be done carefully. 

That’s why it’s best to let professionals handle an air conditioning repair, like RepairSmith.

RepairSmith is a mobile auto maintenance and repair solution available throughout the week with an easy online booking process. If you need an AC recharge service or a fix for your compressor, get in touch with us.

Our ASE-certified mechanics will come over to ensure your AC unit doesn’t blow hot air!