There are various makes and types of compressors used in automotive air conditioning systems operating on R134a. The internal design could be Piston, Scroll, Wobble plate, Variable stroke or Vane. Regardless, all operate as the pump in the A/C system to keep the R134a and lubricating oil circulating, and to increase the refrigerant pressure and thus temperature.
SANDEN – WOBBLE PLATE
A reciprocating piston, fixed displacement compressor. The pistons are operated by a wobble plate, which moves them backwards and forwards in the cylinders. As the front shaft turns the wobble plate angle changes, causing the pistons to move in and out, pulling refrigerant vapor in through the suction side, compressing it and discharging this high pressure vapor into the condenser.
COMPRESSOR MODELS COVERED
BASIC COMPRESSOR SPECIFICATIONS
The clutch is designed to connect the rotor pulley to the compressor input shaft when the field coil is energized. The clutch is used to transmit the power from the engine crankshaft to the compressor by means of a drive belt. When the clutch is not engaged the compressor shaft does not rotate and refrigerant does not circulate the rotor pulley free wheels. The field coil is actually an electromagnet, once energized it draws the pressure plate towards it, locking the rotor pulley and the pressure plate together causing the compressor internals to turn, creating pressure and circulating refrigerant.
R134a is part of the air conditioners lubrication system. NEVER operate an A/C system without refrigerant as there will be no lubrication for the compressor and internal damage will occur. Refrigerant oil is circulated around the A/C system saturated in the refrigerant.
REFRIGERANT CHARGES 24 OZ. TO 40 OZ.
• 135cc oil TXV systems
• 240 cc oil in orifice tube systems
Evacuation is the process of removing air and moisture from the refrigeration system before charging the system with refrigerant. Air or moisture remaining in the system before and during the refrigerant charge process will cause increased pressures during operation resulting in reduced or poor cooling and greatly reduce the compressor life.
EXPLANATION OF EVACUATION:
As vacuum is increased the temperature at which water boils drops. As the water/moisture boils its vapor can be drawn out of the system by the vacuum pump. It is recommended to perform the evacuation process in a warm area. The vehicle engine can also be run in order to warm up the components of the A/C system to enhance the evacuation process.
Other reasons a vacuum cannot be held for 10 minutes after shut off:
· Flush was not completely removed from system before evacuation started.
· Refrigerant is trapped in refrigerant oil from previous charge.
Allow the vacuum pump to run for 30 minutes drawing down near to 30” Hg. After 30 minutes of evacuation close the service valves and turn off the pump. Let the system sit for 10 minutes, if vacuum loss of 2” or greater occurs there is probably a leak.
THROUGH HIGH SIDE WITH A/C SYSTEM OFF:
Charge systems that heat the refrigerant will force the correct charge amount into the system. Once the full charge has been dispensed the service valve must be closed and the A/C system can be started.
THROUGH LOW SIDE WITH A/C SYSTEM RUNNING:
Charge systems with out heating capability will have to use A/C compressor to pull the required charge from the charge system. When charging thought the suction side always use gas from the top of the charge system. Liquid refrigerant charged into the suction line can cause damage to compressor valves.
Before disconnecting any lines or removing the oil plug, always make sure refrigerant has been removed from the A/C system by recovering it with the appropriate recovery equipment.
When working on compressors, separate from the system, always be sure to relieve internal pressure first. Internal compressor pressure can be relieved by removing shipping caps / pads from both ports.
RECOVERY OF REFRIGERANT
Never discharge refrigerant to the atmosphere. Always use approved refrigerant recovery / recycling equipment to capture refrigerant which is removed from the A/C system. Do not mix refrigerants in the same piece of equipment; one should be designated for R-12 and another for R-134a.
Keep refrigerants and oils away from open flames. Refrigerants can produce poisonous gasses in the presence of a flame. Work in a well-ventilated area.
AVOID USE OF COMPRESSED AIR
Do not introduce compressed air into an A/C system due to the danger of contamination.
R134A/PAG OIL HANDLING PRECAUTIONS
This section focuses on service information for Sanden compressors intended for use with R134a and PAG oils.
1. Always follow safety precautions.
2. Do not discharge R134a into the atmosphere. Even though its ozone depletion potential is zero, it does have global warming potential. Recovery and recycling are mandated by the Clean Air Act. Use recovery equipment designated only for R134a. Never introduce another refrigerant into the R134a equipment.
3. Never mix R134a with other refrigerants or A/C systems failure may to occur.
4. Use only Sanden specified PAG lubricants for R134a systems using Sanden compressors. If other lubricants are used, A/C system failure is likely to occur.
5. The Sanden specified PAG oils used in R134a systems absorb atmospheric moisture very quickly. Moisture in the A/C system can cause major damage or failure.
• Never leave PAG oil exposed to air for a prolonged time. Tightly reseal the oil container immediately after each use.
• During A/C system repair, cap all fittings as soon as opened and leave capped until just before they are reconnected.
• If a repair is performed on an R134a compressor or system, evacuate the system for at least 30 minutes before recharging to ensure the removal of moisture which may have been absorbed by the PAG oil in the compressor and system.
Compressor can be rotated 90° clock wise or counter clockwise keeping the oil fill plug above the 3:00 or 9:00 positions.
MOUNTING EAR DEFLECTION:
Total combined ear deflection or bending cannot exceed .4 mm (.016 in) or .2 mm per ear. Mounting brackets allowing extreme ear bending will cause gaskets to leak refrigerant leak.
Information directly from Sanden’s SD Compressor Service Guide
If you have a noisy compressor it is due to improper charging of refrigerant. An overcharged compressor can cause rattling. If charged with pure liquid (this will void the warranty), there is a high probability you have bent reed valves and that’s what is causing a tapping sound.
COMPRESSOR NOT ENGAGING
Compressor clutch is not receiving 12 volts. Check mode operations at controls. Pressure switch not allowing to engage due to pressures too high or too low – check pressures.
COMPRESSOR DISPLACEMENT REGULATOR VALVE DEFECTIVE (VARIABLE DISPLACEMENT COMPRESSORS ONLY)
1. Valve blocked by impurities (the evaporator tends to freeze) = recover refrigerant from the system
2. Regulator springs of the valve improperly set = replace the displacement regulator valve located in the compressor rear cover
3. Evacuate the incondensable gases and moisture from the system by letting the vacuum pump run at least 30 minutes
4. Restore the recommended amount of refrigerant to the system as well as any oil recovered together with the refrigerant
Overheating is most often caused by loss of refrigerant charge. Cool suction side refrigerant returning from the evaporator provides cooling for the compressor. Once the refrigerant charge is lost there is no refrigerant entering the compressor, hence no compressor cooling. Blockages in the system will also prevent cool refrigerant flow to the compressor.
NORMAL CENTER BALL & GEAR SET
OVERHEATED CENTER BALL & GEAR SET
There are several types of contamination the most common are:
• Foreign material like metal chips, dirt and desiccant. Resulting in broken internal compressor components eventually locking up the compressor
• Moisture from improper evacuation or hose permeation. Moisture will corrode internal parts resulting in failure. Moisture will create higher system pressures or freeze in the expansion device and blocking refrigerant flow.
• A/C system flush
The compressor clutch is simply two friction surfaces forced together, like a set of brakes. Each time the clutch is engaged some amount heat is generated. If the engagements occur rapidly or the system voltage is to low, excessive heat created will cause failure of bearing seals and or melting of the field coil epoxy.
HANDLING OR IMPACT DAMAGE
Striking, dropping or over torque will result in these types of damage: