The air conditioner in an automobile uses several components that work in conjunction with each other to provide cool air to the cab of the vehicle. One of those components is the compressor clutch. The clutch allows the compressor to send refrigerant to the evaporator, where it is cooled and sent into the vents. If the clutch begins to make an unusual noise, then one of the parts inside the clutch has a problem.
A common culprit for air conditioner clutch noise comes from a failed bearing. The bearing will make a loud popping or cracking noise when the component has failed or is failing. A bearing will fail when too much heat is created from the clutch. The heat causes the lubrication within the bearing to burn off or deteriorate quickly. Once the lubrication is gone, the bearing will fail quickly, creating a noise even when the air conditioner is not running.
The air conditioner clutch will begin to hum when the motor of the compressor has a problem. Since the clutch drives the compressor, a faulty compressor will cause the clutch to make a noise when the compressor is attempting to engage, but cannot because of a power loss. If the compressor has a short or is not getting the required voltage, then the clutch will begin to hum.
You may hear a scratching or sliding noise when the clutch begins to slip. One reason is that the clutch plate is worn. Another cause for a slipping clutch is an unburnished clutch, which produces a low torque. Burnishing cycles the clutch and allows the surface to wear consistently all the way around the clutch plates. A clutch that is not burnished wears unevenly, which creates a gap between the plates and causes the clutch to slip. If you are replacing a clutch, then bring the new clutch up to the proper torque capacity to prevent this problem from occurring.
A whining noise is created when the serpentine belt is not tightened properly onto the air conditioner clutch. The whine comes from the belt slipping through the clutch pulley. Serpentine belts deteriorate over time and commonly wear or stretch. Once the belt stretches too much, the tensioner cannot maintain a tight fit of the belt to the engine pulleys. The belt begins to slip through all the pulleys, making a whining noise. The clutch will engage the compressor, then disengage the compressor when this occurs. The temperature inside the cab of the vehicle will be cool one moment and warm the next moment.
