How to Jump AC Compressor Clutch Correctly

If your AC clutch is not engaging in your car, this article is for you. We shall discuss the AC compressor, AC clutch, and problems related to the two components. Several possibilities can lead to AC compressor clutch failure. They range from simple to more complicated reasons. Once you read this article, you will be able to diagnose and know the reason behind the failure. You will also learn how to jump AC compressor clutch to prevent you from getting into sudden AC compressor clutch failures.

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What Causes AC Clutch Not to Engage?

Before we get into details on the reasons for the AC clutch not engaging, it is crucial to have some information about the AC clutch.

An AC clutch is what makes the AC compressor turn. It is connected to the flywheel with an accessory belt, and that is how it gets its power. The AC clutch is controlled by a clutch system. The shaft is joined to the flywheel’s rotating shaft by an electromagnetic switch. The AC clutch is a part of the AC compressor, the heart of the Air conditioning system. Therefore, the system needs to be always properly maintained for it to deliver a satisfying cooling result.

When using the car’s air conditioner, its air condition compressor must be activated. As we stated earlier, to start the compressor turning, the clutch must be energized and engaged to the spinning pulley. The compressor clutch consists of a friction plate positioned adjacent to an electromagnetic coil. When the user presses the AC button, the electromagnetic coil is energized and attached to the pump rotor by a strong electromagnetic force. It subsequently makes the compressor turn and compresses the refrigerant.

Now that we have understood about an AC clutch and how does it work? Let us now discuss reasons that may cause the AC clutch not to engage.

Read Also: Why is My Car Air Conditioner Not Blowing Cold Air?

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Insufficient AC compressor oil

Like any other mechanical device, the AC compressor must have a lubricant between its internal parts to prevent metal-to-metal contact. This is the work of oil in the compressor. Therefore, if the oil level is getting low, the AC will automatically shut the compressor off.

Excess Refrigerant: If the system has refrigerant overcharge, the clutch will not be engaged. This prevents the temperature from rising and damages the compressor. AC systems must have a certain amount of refrigerant charge to operate properly.

Low Refrigerant

This is the common reason why the AC clutch is not engaging. When the refrigerant level goes low, the low-pressure switch prevents the compressor from rotating. It, therefore, fails to protect the internal parts of the compressor from getting damaged.

Lockout on Clutch Sensors: Most modern cars have their AC clutches turned ON and OFF using high-pressure and low-pressure switches, and the level of the compressor oil. If one of these three aspects has defected, then the clutch will never be engaged.

Burnt Fuse/Bad Relay

In your car’s fuse box, locate the air conditioning fuse and take it out. Test it is using a multimeter to make sure it is working properly. This is also the same way how to test the ac clutch relay.

How to Examine the AC Compressor Clutch?

Suppose the compressor clutch is not engaging; this is how to check the AC compressor clutch. If the pump is not working, the compressor will not turn. When this happens, it means that there is no refrigerant circulating inside the whole system, and the AC system will not work properly.

Examining the AC compressor is not a challenging task. First, turn ON the AC and fan to the maximum. Start the engine, and then see if the clutch and the pulley are running. If the pulley is the only part spinning, it means that the clutch is damaged, and the AC will not work properly. Let us now learn how to manually engage the AC compressor clutch.

Read Also: Car overheats when AC is on and idle [ Symptoms and Solutions]

How to Jump AC Compressor Clutch

Disconnect Clutch Oil Cable

As we discussed what can make the clutch not engage properly, one of them was high/low oil pressure switches that prevent the compressor from being damaged due to bad operating conditions. Therefore, to check whether the compressor has gone bad or not, disconnect its connector cable from other parts. Using a voltammeter, connect it to the connector and measure the battery voltage and the ground. If there are no readings, then you need to check the AC relay and fuse.

Make Sure the Compressor Have Sufficient Oil

One of the mandatory checks before engaging the clutch manually is the presence of a certain level of oil in the AC compressor. This can be seen from the glass display in the compressor. Check the correct level by making it above the red line. If the oil is insufficient, add some oil with the same specs as the user manual states.

Set the Amount of Refrigerant

The AC compressor should have a certain amount of refrigerant that meets the manufacturer’s requirements. This makes the ideal load on the internal compressor parts and prevents them from damage. Measure the refrigerant with the pressure gauge installed on the high-pressure and low-pressure rail of the AC. Compare it with the recommended value and tries to balance them.

Jump Start the Clutch

After making all the above checks, you need to know how to engage the clutch manually. At the compressor’s front side, unplug the single wire connector; attach a jumper wire to the wire you just disconnected from the compressor. Attach the other jumper’s end to the car battery’s positive terminal, and it will help the compressor start manually.

Read Also: How Often To Change Cabin Air Filter – Everything You Need To Know

Frequently Asked Questions (FAQs)

Q. How Do You Manually Engage the AC Compressor Clutch?

If the AC compressor clutch doesn’t engage automatically when turning on the AC switch in the car AC panel, you need to check the refrigerator and compressor oil levels. At the compressor’s front side, unplug the single wire connector, take a jumper wire and attach it to the wire that you just disconnected from the compressor. Connect the other end of the jumper’s wire to the positive terminal of the car battery. This will enable the compressor to start manually.

Q. How Do I Know If My AC Clutch Relay Is Bad?

Several indicators may help you to know when the AC clutch relay is bad. The most obvious sign of a bad AC clutch relay is that the AC compressor is not turning ON. Normally, you will hear a click sound when the clutch is connected.

If you fail to hear this clicking sound, it is an indicator that the compressor is not getting enough power as a result of a failed relay. Another sign of a failed clutch relay is if there is no air coming out from the AC. If the clutch relay goes bad, the compressor fails to operate, preventing the AC from producing cold air.

Q. Should AC Compressor Clutch Spin Freely?

The AC compressor clutch can spin freely when fully disengaged. It will also spin freely when the compressor and the pulley are engaged. However, if the AC compressor clutch spins freely every time and the compressor fails to turn on, it is an indicator that it is not engaging and it requires replacement.

Q. Will My AC Clutch Engage With Low Freon?

No, the AC clutch will not engage when the Freon is empty or low. The low-pressure switch will prevent the AC clutch from being engaged, and the compressor will not spin. This prevents the compressor from engaging. The major reason the Freon is low would be due to leakage. Once you refill the Freon, check for any leakages to prevent the problem from reoccurring.

Final Words:

Diagnosing what is happening in your compressor is not a hard task. All you have to do is to follow the inspection steps, and you will understand its cause. In case you get confused, do not hesitate to reach the nearest mechanic or expert to get your car fixed, for this will save you cost and time. It is recommendable to make a periodic inspection on the compressor oil and the refrigerator level to prevent yourself from getting into problems.

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Hi there, I am R. Hasan Tito, a mechanic, and owner of this website. My friend and I created this website to share our knowledge, expertise, and experience with our fellow mechanics' community and car users. I am a specialist and certified automotive mechanic (Both Heavy Commercial and Private Cars). I worked as a Mechanic and Mechanic Supervisor for over fifteen years at Global Rebound Automotive companies - Toyota, TATA, BMW, Nissan, TVs, and Others. Now, I enjoy my new role of leading a team of automotive experts (in their respective fields) and publish new content on a regular basis on my website and social media.

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