MACS Monthly Newsletter - 2020 - AUG1

Total Vehicle Climate and Thermal ManagementTM
By Paul Weissler, MACS Senior Technical Correspondent

August 2020

FINDING THE LEAK
you will have to wait a half hour or so, depending on the configuration of the lines and components of the refrigerant system.
It may be helpful (if you can) to run the A/C compressor at as

techinfo.toyota.com

You may be thinking, "Hasn't everything that needs to be
said about the subject of A/C oil leaks already been said, certainly by MACS Service Reports?" But it seems there's always
something new to discuss.
As most technicians (we hope) have heard, late-model compressors incorporate oil separators, the object of which is to keep
the oil in the compressor, rather than in circulation with the
refrigerant. The concept is hardly new, as the legendary General Motors A6 compressor incorporated a small oil pump that
performed this function. On late models, the incorporation of
oil separators reduces compressor pumping energy, which improves vehicle fuel economy, and contributes to the vehicle's
CAFE (Corporate Average Fuel Economy). The current compressor designs don't use an oil pump, which would raise a
packaging issue. Instead, the compressor has a flow passage
that directs refrigerant flow into the separator chamber, where it
causes a cylinder to rotate, producing centrifugal force that separates the oil and refrigerant. The refrigerant flows through the
discharge port into the A/C discharge line into the condenser.
The oil, however, circulates within the compressor, lubricating
its moving parts. See Figure 1.
The logical question: If oil circulation with the refrigerant is
eliminated, what's the effect on trace dye, which as you realize, mixes with the oil. And it is this mixture that shows up at
the leak site, enabling the technician with the black or blue light
(and dye trace enhancing goggles) to find it. The happy answer
to this issue is that the separators aren't 100% efficient, in fact
typically not even 90%. So, the dye producers assure us, trace
dye still works. Any increase in the time for a leak to show up
should be relatively small. Yes, if you inject a dose of trace dye,

Figure 1: DENSO piston compressor has built-in oil separator as shown. Parts are: 13) separator assembly, 14)
separator chamber, 15) separator cylinder. Refrigerant
flows into chamber, causing cylinder to rotate, producing
centrifugal force that separates oil from refrigerant and oil
lubricates compressor parts. "A" is compressor for 2.5-liter
four; "B" is 3.5-liter V-6. Other parts: 1) pulley, 2) clutch,
3) lock sensor, 4) lug plate, 5) crank chamber, 6) shoe, 7)
swashplate, 8) piston, 9) cylinder, 10) solenoid valve assembly, 11) shaft, 12) mass flow sensor, 16) variable suction throttle.

ALSO INSIDE THIS ISSUE:
A/C FITTINGS AND SEALS ............................................................................................................................................... 3
JUST ONE FAN BUT... ..................................................................................................................................................... 5
EVAPORATOR DRAINS .................................................................................................................................................... 7
MAYBE THE "EASY" WAY ISN'T ..................................................................................................................................... 8

MACS Service Reports is the official technical publication of the Mobile Air Conditioning Society Worldwide, Inc., P.O. Box 88, Lansdale, PA 19446. The material published in MACS Service Reports expresses the views of the contributors
and not necessarily that of MACS. Every attempt has been made to ensure

August 2020

the accuracy of the content of MACS Service Reports. MACS, however, will
not be responsible for the accuracy of the information published nor will MACS
Worldwide be liable in any way for injury, labor, parts or other expenses resulting
from the use of information appearing in MACS Service Reports.

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MACS Monthly Newsletter - 2020

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