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Hi,
There are swash-plate and wobble-plate designs used in reciprocating AC compressors.
Zexel/Diesel-Kiki/Denso/Seltec/Tama use the swash-plate design, whereas Sanden uses the wobble design. Each design has its own pro and cons but both had served the mobile AC community well so far.
In swash-plate design the pistons are directly driven by the plate via half-moon bearings. This design exerts more stress on these bearings due to the sliding motion of the plate is converted to moving the pistons. This requires anti-wear additive (or high stress lubricant) in the refrigerant oil. A check on Denso's oil MSDS (search for Denso ND-8 oil MSDS for example) shows the presence of this additive i.e Tricresyl phosphate. The good thing is that this design is more compact and space-saving than the wobble-plate variety.
Currently I'm using ND-8 oil in my Zexel compressor and the AC load on the engine is much less than before (I had used Supercool PAG46 oil before). This oil's viscosity is ISO46 which is well suited for the Zexel. Another good oil with anti-wear additive is the Idemitsu Daphne Hermetic series used in Ford FS10 compressor (swash-plate design) in many non-Volvo applications (e.g. Korean cars).
In the wobble-plate design (Sanden) the pistons are driven by rods that are attached to the plate. Apparently this design reduces much friction in the compressor and the AC load on the engine is much less. A search for Sanden SP-10 oil MSDS for example shows no anti-wear additive being used. Unfortunately even if this appears to be the better design here, there are reasons that could lead to its unavailability at the local parts store or the internet. Thus some users (like me) are stuck with the swash-plate variety.
It helps to know the exact model number and make of the compressor, then determine whether its wobble or swash plate design, choose the proper refrigerant oil (with anti-wear or not) and lastly choose the proper oil viscosity required for the compressor.
For R134a use the preferred oil is PAG. For R12 to R134a conversion the preferred oil is ester i.e POE, as ester oil can mix with residual mineral oil used in R12.
To the OP:
As your current compressor had seized the system must be flushed. No shortcuts about this. Installing new compressor of whatever make without flushing might get you back to same seizing later. Granted that some R12 to R134a conversion might got away without proper flushing but this is not your situation. Better refer this to AC specialist for flushing and install the system clean with proper PAG oil required for the new compressor and charge the system. And choose double end capped (DEC) PAG oil for the purpose as this oil absorbs less moisture than single end capped (SEC) oils. For instance, both ND-8 and SP-10 are DEC oils.
SEC oils may be part of the R134a moisture-absorbing design last time as it also helps to absorb residual moisture after vacuuming. Thus the filter-drier had less job to do. But absorbing moisture causes the oil to become a weak acid which might eat away the insides of those aluminium AC components resulting in a leak later.
There is no specific AC compressor to "avoid" in your selection. With proper installation - clean system, correct refrigerant oil, new filter-drier, vacuuming, charging with proper R134a weight (this also to ensure adequate oil return to lubricate the compressor) - there should be no problem in the long run.
Regards,
Amarin.
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