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DIY Mercedes AC Recharge – HowTo the easy way

mercedes benz ac rechargeThe hot summer days are here and you realize that the air conditioner on your Mercedes-Benz is no longer blowing cold air. A/C problems can be complicated but they also can be something as simple as the system being low on freon. This is usually one of the most common problems. The solution is simple: your air conditioning system may need recharging. In many cases you can add R134a refrigerant and your system is back to working normally again. In this step-by-step guide, we will show you how to recharge the A/C system using an R134a recharging kit. This method is used to top off an A/C system that has been working fine for 5 or 6 years. Topping off a system that is over 5 years old is normal as long as there are no major leaks or defective components. 

The purpose of this guide is to address the following:

  • Mercedes-Benz needs AC recharge
  • Mercedes AC blows hot air
  • Mercedes air conditioner needs service
  • Aircon Recharge DIY
  • How to recharge Mercedes A/C yourself
  • Auto A/C Service
  • Choosing the best R134a freon refrigerant
  • A/C or Econ light is flashing or on

What is the best R134a recharging kit for Mercedes-Benz?

There are so many recharge kits on the market that makes it is difficult to choose which is the best R134a refrigerant. It is important to understand that all R134a is basically the same, what is important is what else has been added to the R134a. There are a few things more important than “Super ice cold, sub zero” labels.

What to look for when choosing an R134a recharging kit or also known as an aircon regas kit. Look at the can and you will see some of the following labels or none of them if it is just simply R134a with no additives.

As you choose an A/C recharge kit keep these questions in mind.

Do I need the A/C recharge kit to have?

  • Oil mixed to help with the lubrification
  • Leak sealer to help prevent small leaks
  • A/C dye to help a mechanic easily find leaks
  • Reusable dispenser and gauge
  • Adjustable temperature gauge that can help you fill the a/c properly.
Now it is up to you what you will like to add the air condition system of your Mercedes-Benz, which depends on your situation. If you suspect a small leak you can use a refrigerant kit with a leak sealer, if you have a large leak then skip the small leak recharge kit and go for an aircon regas kit that has dye in it. Or if you know you have a seal-proof system or don’t like the idea of adding these additives into the expensive Mercedes-Benz  A/C climate control system, then adding pure R134a or just one with only added oil will be the safest way to go.

Recommended R134 A/C refrigerant kits for aircon refill?

There are no best A/C refrigerant kits, as that depends on your needs as described above. With that said here are a few kits that are highly ranked and affordable. If you are interested in any of them, links have been provided for you to read reviews and check current prices on Amazon.

A/C PRO ACP-100 Professional Formula R-134a Ultra Synthetic Air Conditioning Refrigerant
  • Reusable dispenser and gauge
  • Temperature adjustment gauge
  • Larger than other aircon kits – 20 oz
Interdynamics MAC-134 EZ Chill Refrigerant Refill
  • Charging Gauge
  • Added oil
  • Leak Sealer
  • Size – 18 oz
3 Cans R-134a DuPont Suva A/C Automotive Refrigerant/Freon R134a
  • Just R134a refrigerant nothing else
  • Meets AHRI-700 and SAE J2776 Purity Standards
  • By Dupont the R-134a inventors
  • Great Price


Of course, you can choose any kit that you prefer. These are some of the most popular kits. Now let’s move on to how to charge your AC system.

Instructions on how to charge the A/C in your Mercedes-Benz

This video shows how to recharge the air conditioner on your Mercedes-Benz. Charging the system with a refrigerant charging kit can take between 5 to 10 minutes depending on the system’s capacity.

Before we begin, remember: These instructions may vary depending on the AC recharge kit that you are using. Be sure to always read the instruction notes on your recharging kit. The gauge that you will see in our video is similar to the gauge found on one of top selling A/C recharge kits, the A/C PRO ACP-100.

  1. Turn the engine on and let it idle. Turn the air conditioner ON and set it to the maximum cooling setting.
  2. Open the hood of your VEHICLE and locate the low-pressure AC service port and remove the cap.ac low charging port location
  3. Attach the refrigerant gauge to the service port. You will need to press and hold the quick-release at the end of the hose, insert it into the AC charging port then release it.
  4. Rotate the dial on the lens until the red arrow in the middle of the V is pointing to the temperature corresponding with the outside temperature. If the pressure is below the range of the V and the air climate control is blowing hot air that means the system is low on refrigerant and you can proceed with charging the system.
  5. Read the pressure in your air conditioner system. If the pressure is low the gauge reading will be in the white zone. If the pressure is normal then the gauge should be in the green zone. You should not have a reading on the HIGH / RED zone except when the car is turned off, in which case it is normal.
  6. Always keep the can UPRIGHT. As you charge the system shake the can slightly every two or three seconds while you are charging.
  7. Every 30 seconds release the trigger to stop the charging process and read the pressure. Be careful to not overcharge the system. On our gauge overcharging was marked in red. Note that the system may show overcharged with the engine turned off and that is normal.
  8. Stop recharging the system when the pressure gauge shows within range. 
  9. Detach the connector from the low-pressure AC port. Reinstall the cap, close the hood, and enjoy your A/C system again.


  • DO NOT TURN THE CAN UPSIDE DOWN WHILE CHARGING. Only gas should go into the AC system, by turning the can upside down the AC system will get liquid refrigerant which can cause the AC compressor to lock up and also wash out the oil. Keep the AC refrigerant can in the up position and only shake it slightly while charging.
  • If the refrigerant level is very low, the AC compressor will not engage. Charge the AC system for a couple of minutes with the engine running, and you should notice the AC compressor engages/kick in once you add enough refrigerant into the system.
  • Once the A/C kicks in and the air conditioning system starts to work the pressure on the system may drop. Continue to add freon until the system shows pressure on the correct range correlating to the outside temperature.

What if your Mercedes-Benz A/C doesn’t work after a recharge?

If you used a recharge kit to top off your A/C system but the air conditioner still doesn’t blow cold air then it may be time to take your car into an auto repair shop for an A/C diagnosis. A professional needs to perform a dye test and check the system for leaks.

Mercedes-Benz Air Conditioning Service Cost

A Mercedes-Benz specialized shop may charge you between $100-$150 to diagnose your A/C system.

Important factors to keep in mind when charging the A/C system are:

  • Ensure the system is sealed and not leaking.
  • Ensure the system does not have any moisture or air in it. An A/C vacuum pump is needed to achieving this.
  • Ensure the compressor is operating correctly. Including the serpentine belt. Make sure the cooling fans work.
  • Clean out the condenser by the radiator! Dirt and leaves build up in there over the years. Take a garden hose and clean it.
  • Add the correct refrigerant amount. Don’t guess! There is a label under the hood that tells you how much to add.
  • Do not introduce liquid R-134a into the system. Only gas should enter via the A/C low-pressure charging port.

AC Light Flashing on my Mercedes-Benz

When you attach the gauge, the pressure is in the red zone.

This may happen because the engine is off or the A/C compressor is not engaged.

You measure the aircon gas pressure and the gauge shows zero.

This could happen because the system is very low on refrigerant. It could be that the system has a major leak.

When did Mercedes-Benz switch to R-134a refrigerant?

Mercedes-Benz switched to R-134a in the early 1990s. Look under the hood to see what refrigerant your air conditioner system uses. If you have an older Mercedes-Benz you may need to use R-12 which you can also find online here.

My gauge doesn’t have a temperature gauge for the outside temperature. How do I know how much R-134a refrigerant to add?

R-134a System pressure chart.

r134a remperature pressure chart
R-134a Temperature Pressure Chart based on the outside temperature. Source: ACProCold.com

Recharging Mercedes-Benz A/C. Where to connect?

There are a couple of tools online that could help you locate the A/C low-pressure charging port on your Mercedes-Benz

ac low charging port location
Location of AC low-pressure charging port on C-Class W203
ml320 W163 A/C charging port location
Location of A/C Charging Port on ML Class W163

One comment

  1. Thanks for your advice and helping me keep enjoying my old SL

    Nearest M-B shop is hours away and word is that they are not very proficient but do know how to charge.

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