MB Medic Mercedes-Benz Repair Guides, Service, How To DIY
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If the Air Conditioner on your 2000-2006 Mercedes-Benz S-Class W220 is not working, you can try refilling the system with R134a refrigerant. If the refrigerant level in the system gets too low, which is a common problem in older cars, the Air Conditioner Control Unit shuts off the A/C to protect it from damage. In many cases, refilling your car with refrigerant will fix the A/C blowing hot air problem. This guide is specific to the W220; the general Mercedes A/C recharge guide covers other models.
Parts Required
Here are a few R134a A/C refrigerant refill kits that will do this job. The links go to Amazon so you can read reviews and check current prices.
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A/C PRO ACP-100 Professional Formula R-134a Ultra Synthetic Air Conditioning Refrigerant
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Interdynamics MAC-134 EZ Chill Refrigerant Refill
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3 Cans R-134a DuPont Suva A/C Automotive Refrigerant/Freon R134a
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One note on kits that include a leak sealer. The sealer is meant to plug a small leak from the inside, but it can also block the expansion valve, and it contaminates the recovery machine a shop connects later, so many shops will not touch a system that has had sealer in it. If you may ever pay someone to repair the system properly, use plain refrigerant.
How to charge the A/C in your Mercedes-Benz S-Class W220
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 and 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 R134a refrigerant kit. The gauge that you will see in our video is similar to the gauge found on the A/C PRO ACP-100 kit listed above.
Safety first. Escaping refrigerant is cold enough to freeze skin and can blind you, so wear safety glasses and gloves and keep your face away from the fitting when you connect or disconnect it. The kit’s coupler is made to fit only the low pressure port; if it will not snap on, you are on the wrong port, so never force it onto the high pressure side. The engine runs during this job, so keep your hands, the hose and the gauge clear of the belt and the cooling fan. Do not vent refrigerant into the air; releasing R134a on purpose is illegal in the United States.
- Turn the engine on and let it idle. Then, turn the air conditioner on and set it to the maximum cooling setting.
- Open the hood of your S-Class and locate the low-pressure AC service port, and remove the cap.
- 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.
- Rotate the dial on the lens until the red arrow in the middle of the V points 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 it.
- 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 in the HIGH / RED zone except when the car is turned off, in which case it is normal.
- Always keep the can upright. As you charge the system, shake the can slightly every two or three seconds.
- Every 30 seconds, release the trigger to stop the charging process and read the pressure. Be careful not to overcharge the system. On our gauge, overcharging was marked in red. Note that the system may show overcharged with the engine turned off, which is normal.
- Stop recharging the system when the pressure needle is within the V range in the green zone.
- Detach the connector from the low-pressure AC port. Reinstall the cap, close the hood, and enjoy your A/C system again.
Important Notes
- DO NOT TURN THE CAN UPSIDE DOWN WHILE CHARGING. Only gas should go into the AC system. If you turn 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 upright position and only shake it slightly while charging.
- If the refrigerant level is very low, the AC compressor will not engage, because the low pressure switch keeps it off to protect it. If it still does not engage once the pressure is back in range, read our guide to diagnosing A/C compressor clutch problems before adding anything more. Charge the AC system for a couple of minutes with the engine running, and you should notice the compressor engage/kick in once you add enough refrigerant to 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 in the correct range relating to the outside temperature.
W220 S-Class A/C Hidden Menu
Like in other Mercedes-Benz models, climate control can be used to troubleshoot the A/C system. To troubleshoot your S-Class via the climate control display, you need to enter the secret/hidden air conditioning diagnostic menu. If you want to learn how to do that, read this article: How to Access the A/C Hidden Menu on the W220.
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 to 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 and $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. Do not guess! There is a label under the hood that tells you how much the system holds. That figure is the charge by weight for a full evacuate and recharge; a top off from a can cannot measure weight, which is why the method above charges to the gauge pressure for the outside temperature and stops as soon as the needle reaches the range, rather than adding more.
- 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
If the A/C light on the Climate Control is flashing, it means that the air conditioner control unit has a fault code. To find out what the problem is, you will need a diagnostic scanner that can read fault codes.
The gauge is in the red zone as soon as you attach it
This may happen because the engine is off or the A/C compressor is not engaged. It is normal for the pressure to be high when the engine is turned off. It should not be high when the compressor is engaged.
The gauge shows zero
This means the system is empty, and an empty system has had air and moisture in it. Charging a can into it will not last, and the moisture damages the compressor and the dryer, so do not start charging. The system needs the leak found and fixed, then a vacuum pulled with an A/C vacuum pump, and only then a charge by weight. An auto repair mechanic will have to perform a dye leak test to find the leak.
When a Recharge Does Not Fix It
A can of refrigerant fixes exactly one problem, a system that has slowly lost charge through its seals. If the air is still warm with the pressure in range, or the A/C light is flashing, the climate control unit has already decided something is wrong and stored a fault saying what. On the W220 the climate control unit is not an emissions module, so a basic OBD2 code reader cannot see it at all; it shows the engine codes and reports the car clean. The hidden menu described above gets you part of the way, and our guide to Mercedes A/C diagnostics and trouble codes explains what the stored codes mean. A full system scanner that reads the climate control module, such as the YOUCANIC UCAN-II Pro, shows the fault itself, lets you see whether the compressor clutch is being commanded on, and clears the code after the repair so the light stops flashing for a reason rather than for a moment. Read the module before you buy a second can.
Before you buy parts, scan every control module, not just the engine. It shows the root fault behind the warning lights and tells you whether the problem is still active. See how to do a full health check.
