compressor oil question

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compressor oil question

Postby cornbinder89 » Sat Jun 11, 2016 9:28 pm

As most know, a A/C compressor has no oil control ring, unlike an engine or air compressor. The question is why, or why not? The only two answers that make sense to me are 1) by circulating with the refrigerant, the oil is cooled by the time it returns. and 2) when Tx valves are used, it allows some lube to keep the valve from sticking. Since most new car A/C uses the CCOT with no moving parts, wouldn't it make sense to keep the oil in the compressor sump? If it stayed in the sump, size and finning of the sump could dissipate the heat, negating the need for answer #1
I have one vehicle with the old York style compressor and back-seat service valves. At the beginning of the season, I close the valves (suction 1st, then discharge) and check the oil in the compressor with the service dipstick, top up if required, then evacuate the compressor, and open the valves. It is the only thing I like about that compressor/system. It shakes so much that it snaps the mount bolts off at fairly regular intervals. I carry spare bolts. Every 8 years or so it succeeds in breaking the cast aluminum "mount" that the compressor mount bolts too (Cat 3406B). It is such a common problem that Cat keeps the bracket in stock. The aluminum casting is fairly well anchored, but the shaking of the two cyl recip makes stress fractures over time. Doesn't do it with the axial compressors.
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