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Compressor Seizure
All compressors designed to operate with compressor oil will fail if poor oil/refrigerant input occurs, as the compressor will be inadequately lubricated/cooled. For example, running an engine without oil or refrigerant results in engine failure.

During normal compressor operation, components are lubricated with an oil film that reduces friction and dissipates heat. The compressor circulates a mixture of oil and refrigerant through the AC system. This mixture lubricates and cools the moving internal components. The refrigerant acts as a heat carrier, helping with lubrication and heat dissipation. Poor lubrication leads to increased heat and component expansion. Expansion reduces the clearance around components and eliminates the oil film. Without this oil layer, metal-to-metal contact occurs, causing seizure.

For SDH compressors, typical seizure points are the central bearing and piston rod sockets. Central bearing seizure occurs when the compressor and/or central bearing receive insufficient lubrication and cooling, often resulting in bearing meltdown and welding to fixed gears.

For SDV compressors, the typical seizure area is the balance ring.

  • Compressors identified as manufacturing defects are covered under Sanden’s warranty.

Explanation of AC Failures
For PX compressors, typical seizure areas are piston feet and swash plates.
For TR compressors, typical seizure areas are the center zone of the swash plate.

Seizure occurs due to lack of lubrication and cooling, which may be caused by:

  • Insufficient refrigerant flow due to undercharging.

  • TXV valve blockage or malfunction.

  • Thermostat failure.

  • No airflow to the evaporator (blower motor failure).

  • Refrigerant and/or oil loss due to leaks or oil traps.

  • Lack of return oil caused by long idle times or undercharged system.

  • System blockage due to contamination.

  • Faulty central bearing or contacting gear surfaces.

  • Slow liquid caused by incorrect system charge.

  • Liquid refrigerant flooding the compressor (removes oil film around central bearing while compressor is running).

Clutch Slippage
Clutch slippage occurs when the armature plate fails to properly lock with the clutch rotor and rotate synchronously. This usually happens under high torque conditions, very low voltage supply, or clutch wear. When power is applied, the field coil becomes an electromagnet, magnetizing the clutch rotor and armature plate. Friction and magnetic attraction lock these parts together, turning the compressor shaft.

Clutch slippage specifically describes when the armature plate cannot lock properly with the rotor. The armature plate tends to drag (slip) over the rotor surface, causing intense friction and heat. Continued slipping causes deformation of the armature plate. In rubber-armature clutches, slippage may melt the rubber damper, leading to total clutch failure.

Possible causes of clutch slippage and overheating include:

  • Liquid migration into the crankcase when the AC system is off.

  • Liquid floodback causing high shaft torque that prevents armature plate rotation, leading to slippage.

  • Contaminants on friction surfaces reduce friction coefficient, causing armature slip.

  • Low voltage in field coil reduces magnetic force.

  • Excessive system pressure causing high shaft torque, preventing armature rotation.

  • Faulty motor hardware connections causing insufficient current to the field coil.

Customer Damage
Customer damage describes compressor failures caused by improper installation, poor handling, and/or incorrect system application.

Compressors are vulnerable to damage when the AC system malfunctions. Safety devices such as Pressure Relief Valves (PRV), Thermal Protection Switches (TPS), and High/Low Pressure Cutoffs help reduce compressor damage risk under abnormal system conditions. These devices shut down the system to limit damage.

When analyzing a returned compressor failure, an inspection determines whether the failure was caused by usage damage or faulty installation. If external signs or exposure to extreme conditions are evident, the failure is classified as customer damage.

Customer damage includes but is not limited to:

  • Compressor ear bearing damage caused by incorrect gap between bracket and bearing. Installation bushings may need proper positioning before compressor mounting.

  • Excessive torque applied to hose fittings, causing stripped threads or broken ports.

  • Faulty field service with incorrect part replacements leading to compressor failure. Typical checklist items include:
    – Washing the AC system to prevent oil contamination.
    – Replacing refrigerant and oil.
    – Replacing expansion valve if needed.
    – Repairing all oil leaks.

  • Mechanical damage to clutch parts (scratches, dents, air gap changes, lead wires cut, compressed, or removed).

  • Mechanical damage inside the compressor cylinder block.

  • Addition of unauthorized chemicals that cause system or compressor failure.

  • Improper compressor packaging or transportation.

  • Unauthorized modifications (painting, coating, polishing, etc.).

Moisture Contamination
Moisture contamination refers to failures caused by moisture entering the AC system.

The AC compressor is designed to operate efficiently under specific controlled conditions. Contaminants entering the system reduce compressor efficiency, effectiveness, and durability.

Moisture refers to water in any form (solid, liquid, or gas). When moisture enters the AC system, it can combine with refrigerant to form an acidic solution that corrodes internal compressor components. Moisture does not directly cause compressor failure but causes failure due to corrosion and/or wear weakening parts.

Moisture can form ice at the expansion valve, causing unstable valve operation. This may result in liquid refrigerant flooding the compressor or low refrigerant/oil mix reaching the compressor.

Moisture also causes wear on internal parts such as valve plates.

During normal operation, pistons compress refrigerant gas in cylinders. Presence of moisture can cause liquid slugging. Liquid slugging occurs when liquid refrigerant enters one or more cylinders. Since liquid is incompressible, pistons attempting to compress it can damage compressor seals, cause permanent valve damage, and reduce compressor efficiency.

Moisture contamination occurs due to moisture ingress and retention in the AC system. Causes include:

  • Improper system evacuation (vacuuming).

  • Contaminated system components.

  • Contaminated refrigerant and/or oil.

  • Saturated or faulty moisture traps.

  • Water permeability in hoses.

  • Exposing open hoses or AC components to air for extended periods.

  • Missing suction/discharge valves on compressor.

  • Moisture traps should be replaced according to manufacturer’s recommended service intervals.