The centerball (also known as the centering ball) functions as a pivot point between the pivoting planet plate assembly and the stationary fixed gear. As the compressor shaft rotates, the planet plate swivels / pivots around the fixed gear. The centering ball allows the planet plate to pivot up and down as the shaft rotates. This up and down movement of the planet plate allows the pistons to move up and down in the cylinders.
During normal compressor operation, the centering ball is coated with an oil film which reduces friction and allows for the dissipation of heat. The system refrigerant acts as a heat carrier and aids in the lubrication of and removal of heat from the centerball. Centerball Seizure is a catastrophic condition which results when the compressor and / or centerball is deprived of adequate lubrication and cooling. As the lubrication and / or refrigerant are depleted the friction and temperature of the parts increase rapidly until thermal distortion and parts failure occurs. This failure usually results in the centerball melting and becoming welded to the fixed gear.
Centerball seizure occurs as a result of lack of lubrication and cooling around the centerball. This condition can be caused by the following:
A) TXV blockage or Malfunction.
B) Thermostat failure.
C) No air flow to Evaporator ( Blower fan motor failure
D) Lack of refrigerant and I or oil due to a leak.
E) Lack of return oil due to too long a circuit or system undercharge.
F) Lack of refrigerant flow due to inadequate charge.
G) Blockage in system due to Contamination in system.
H) Defective centerball or gear mating surface.
1) Liquid slugging due to improper system charging.
J) Charging Liquid refrigerant into compressor (washes off oil film from around centerball).
There are 4 primary categories of centerball seizure.
1. Partial Seizure = A partial seizure occurs when the centerball slightly deforms and loosely welds to and then separates from the fixed gear. The shaft may still rotate but the rotation will be rough and often above normal torque requirements.
2. Typical Seizure = A typical seizure occurs when the centerball overheats and completely welds to the fixed gear. This results in zero rotation of the compressor shaft and may often lead to clutch failure as a result of non rotation of the shaft.
3. Meltdown = A meltdown occurs when the overheating is severe enough and prolonged enough to cause complete melting and deformation of the center ball. This condition may also result in both zero rotation of the compressor shaft and possible clutch failure as a result of non rotation of the shaft.
4. Clean Seizure = A clean seizure results when the centerball failure occurs rapidly and with minimal damage to surrounding parts. In most cases the seizure occurs within a few hours of initial compressor engagement. The compressor oil is often clean and free of contamination. There is usually very little evidence of overheating in these cases. Clean seizures are usually the result of assembly and / or material defects or improper system charging.
