Diagnosing A/C Compressor Clutch Problems on your Mercedes-Benz

The A/C system on your Mercedes-Benz includes many sensors and components, including the air conditioner compressor. The A/C compressor is the heart of the system. One crucial element of the air conditioner (A/C) compressor is the clutch.  It is important to understand how to check if the A/C compressor is engaging or not.  

Purpose of the A/C Compressor Clutch

While the A/C compressor on your Mercedes-Benz is an important part of the system,  the A/C compressor clutch is even more important. Every time you want cold air to blow on your Mercedes-Benz cabin, you turn on the climate control and set your desired temperature. The Air Conditioner control unit starts gathering input from an array of sensors on your Mercedes-Benz.

When you turn on the A/C, the clutch engages, and the pistons start to compress the refrigerant.

If no problems are detected, such as low refrigerant in the system, it sends a signal to disengage the A/C compressor clutch. Otherwise, the A/C compressor engages and starts to compress the refrigerant. By compressing the refrigerant, we increase the pressure in the system. The A/C compressor clutch engages to create high pressure in the refrigerant, and its state is controlled by the Air Conditioner Control Unit. If there are error codes on the A/C Control Unit, the compressor will not engage, and you will need to reset the fault codes using a diagnostic scanner such as the YOUCANIC full system scanner.

Test if the A/C compressor clutch is engaging

How do you tell if your A/C compressor clutch is working or engaging? This video is helpful if you are trying to troubleshoot air conditioner problems, the A/C compressor clutch in particular.

1. Start by turning the engine on. Set the A/C to the maximum cold setting.
2. Open the hood and look at the serpentine belt to locate the A/C compressor.
3. Now, look at the pulley of the air conditioner compressor. The center part (the clutch) should be engaged and should be spinning along with the pulley.

The center part on the pulley of the A/C compressor will not spin when you have the air conditioner off or if there is a problem. Once you turn on the AC in the center part of the compressor,  the AC clutch should engage and start to rotate with the pulley. The serpentine belt rides the A/C compressor pulley every time the engine runs, but the A/C compressor only works when the A/C clutch engages it.

Clutch-Less Variable Displacement AC Compressor

Mercedes-Benz has started using clutchless, variable-displacement A/C compressors on many of its late models. A clutchless variable displacement A/C compressor can be found on models such as  W203 C-CLass and W211 E-Class. You will not be able to check the operation of the A/C compressor clutch on these compressors because they don’t have one. The following video explains how the clutchless variable displacement A/C compressors work.

Why does your air conditioner clutch not engage?

When the A/C system doesn’t blow cold air, the first thing to check is whether the compressor engages. If it doesn’t, do not assume that the A/C compressor itself is the problem. Remember that the A/C clutch is controlled by the A/C Control Unit. If that unit detects an error, it will not engage the A/C compressor to avoid it getting damaged. Another reason the A/C compressor may not engage is that the system is low on R134 refrigerant. Typically, older cars may have very slow leaks that may require a top-off with refrigerant every couple of years. You can use an R134a recharge kit to recharge your system if the air conditioning (A/C) compressor is not working. Here are a couple of highly rated kits available on Amazon.

• A/C PRO ACP-100 Professional Formula R-134a Ultra Synthetic Air Conditioning Refrigerant with Reusable Dispenser and Gauge – 20 oz We like the fact that this kit has a gauge for the outside temperature adjustment so that you can know the exact pressure range you need to be on.

• Interdynamics MAC-134 EZ Chill Refrigerant Refill with Charging Hose and Gauge – 18 oz This A/C R134a refrigerant has oil and leak sealer mixed in.

Common A/C Compressor Clutch Problems

Where to buy an A/C compressor Clutch for Mercedes-Benz?

Two of the best places online where you can buy new or used air conditioner compressors or clutches are listed below. If you know of any other resources, please feel free to let us know.

• Check Availability and Price on eBay
• Check Availability and Price on Amazon

What is the Best Scanner for my Mercedes-Benz?

If you’re experiencing problems with your Mercedes-Benz, the YOUCANIC full system diagnostic scanner can provide invaluable assistance in troubleshooting the issues. By connecting to your car’s onboard computer, the scanner can read fault codes and provide detailed information about any problems with your engine, transmission, brakes, and other systems. Additionally, the scanner can perform diagnostic tests on various systems, such as the ABS, airbag, and steering systems, to help identify the underlying cause of any issues.

In addition to providing diagnostic information, the YOUCANIC scanner can also save you time and money on repairs by enabling you to perform simple fixes yourself. For example, if you notice the check engine light on, the scanner can assist you in identifying the problem and determining if it’s a simple issue that you can address at home or if you need to take it to a mechanic. This can help you avoid unnecessary trips to the repair shop, saving you both time and money.

All in all, the YOUCANIC full system diagnostic scanner is a powerful tool that can help you maintain and troubleshoot your Mercedes-Benz. It’s an excellent investment for both DIY mechanics and professional technicians, as it can assist in diagnosing and resolving even the most complex automotive problems with ease, which can potentially save you time and money on costly repairs.