Electromagnetic Clutch Parts
First of all, we need to know each clutch parts terminology. See the following picture:
A Typical Clutch Assembly
CLUTCH RELATED FAILURES
Then, let us focus on the most common symptoms and causes of clutch-related problems.
Burning of the hub, pulley, or coil
Insufficient voltage in the coil can cause the internal windings to overheat and cause the clutch hub to slip on the surface of the pulley. The auto ac compressor is in a faulty state due to slippage or loss of lubrication or running under high-pressure conditions, which will cause the clutch to slip. Slippage occurs continuously during compressor operation and can subject both the clutch and coil to extreme temperatures up to 1200 degrees Fahrenheit. This will quickly burn the clutch and its internal components.
Bearing failures are usually caused by system problems. Few bearings themselves can cause compressor failure or lockup. For example, if the clutch is severely slipped due to high or low-pressure conditions, or due to the perforation of the compressor, the excessive heat generated by the slip will quickly melt and destroy the bearing seal. Then, the bearing loses grease and locks up or falls off, usually damaging the clutch in the process. Since the bearing is not the root cause of the problem, this type of bearing failure is not covered by the warranty. Warranty can only be considered when the bearings are intact and there are no signs of overheating compressor or air conditioning system problems or signs related to installation. There are few manufacturing defects in ac compressor clutch bearings, and warranty allowances are usually only associated with excessive noise symptoms.
If the complaint is only related to noise, the problem may be a damaged clutch pulley bearing. Keep the clutch armature hub fixed, and then only rotate the pulley to check whether the bearing is rough or running poorly. If it is found to be too noisy or difficult to rotate, the bearing may be suspicious. However, as with the bearing failure situations described above, there are several factors that can cause the bearing to become noisy or rough in operation. Rough bearings can also be bearings that are in the early stages of failure due to system problems involving extreme heat. This is usually the case if the car compressor clutch has been running long enough and then becomes noisy. Most factory bearing defects become obvious in the first few hours of compressor operation. Warranty considerations for malfunctioning compressors and clutches are provided only when there is no obvious indication that the malfunction is caused by other factors.
Polishing is the cycle of the clutch to allow wear of the engaging surface area. The reason for polishing the clutch is to increase the initial starting torque. When replacing the compressor or clutch, most technicians fail to follow this important procedure. An unpolished clutch may produce a low-torque state, which can cause the clutch to slip and thus cause malfunction. When replacing the clutch or compressor and clutch assembly, follow this important polishing step. Run the engine at a speed of 1,500 to 2,500 RPM. Use the controls on the dashboard to open and close the clutch at a rate of 10 to 15 times per minute for at least 50 cycles. This will allow the clutch to reach its working torque capacity.
The incorrect air gap between rotor and hub
An incorrect air gap can cause the clutch to engage or disengage incorrectly. This is especially true on Sanden, Seltec and Frigidaire / GMC compressor clutches. Before operating this type of compressor, check the air gap between the hub/armature and rotor/pulley. In the illustrated section of the A/C parts catalog, check the specifications required for your specific type of compressor clutch. These clutches may involve adding or removing shims to properly clearance the hub sleeve. The newly manufactured compressor and clutch assembly have been correctly installed at the factory. Most clutch failures or problems related to incorrect air gaps can be traced to incorrect clutch replacement in the field. Please check if it is applicable before returning to a possible warranty.
Misaligned belts or wrong clutch used
In some cases, a malfunction of the clutch may cause the pulley to slip, tension, or overtighten, or the pulley is not aligned. Further inspection may find that the wrong clutch is installed on the compressor (the installation distance specification is incorrect). Clutches with a misalignment of only 1/8" may cause problems. Poor alignment sometimes occurs due to cracked or loose compressor mounting brackets on the engine. Please check for excessive wear and/or friction Signs of internal signs. Please check the grooves of the pulleys before returning for a possible warranty.
Internal magnetic field open
This situation is rare and can only be verified by removing the clutch pulley and hub from the compressor. The excitation coil core is fixed in place by external epoxy resin. If the bond between the epoxy resin and the winding fails, the coil may move, which may cause the wire of the coil to break, causing the clutch to fail. Except for small cracks around the outer diameter of the epoxy, there are no external signs of a problem. However, the open circuit can be found by the resistance (ohm) meter. If an open circuit is found, and there is no sign of resin melting or installation damage, the coil itself can be guaranteed.
Field coil installation flange welding failed
This situation only applies to CCI / York / Tecumseh type clutches. The excitation coil assembly is composed of a magnetic field core surrounding the coil and a flange mounted on the compressor. The field core and flange are assembled at the factory and connected together by spot welding. Although it rarely occurs, defective spot welding can cause friction between the outside of the excitation core and the inside of the pulley, which will eventually lead to disconnection and inoperability of the clutch. Please note that in most cases, including welding failure and coil flange fracture, there will usually be severe vibration problems. This is especially true on the Detroit 60 series engines. In some cases, the vibration can be so severe that the screws securing the coil to the compressor can loosen, causing the clutch assembly to disengage from the compressor shaft. Without a firm installation, the clutch and coil will actually be torn by the force of the drive belt trying to rotate the clutch pulley. In this process, the compressor shaft is usually also damaged. If this happens, all warranties for the compressor and clutch will be invalidated.
If the wire connected to the excitation coil is faulty, the clutch will not work. This is obvious during installation and rarely happens later. However, there is no obvious evidence that damaged or cut wires are not the cause of the warranty.
Post time: Jun-18-2020