MACS Monthly Newsletter - 2017 - OCT5

the system, so that if a leak should occur down the
road, the dye can leak out with the refrigerant and
oil, and show itself for the technician to find.

means a mechanism which removes at least 50%
of the oil entrained in the oil/refrigerant mixture
exiting the compressor and returns it to the compressor housing or compressor inlet, or a compressor design which does not rely on the circulation
of an oil/refrigerant mixture for lubrication. That's
important, because if the OEM wants to get this
credit, the compressor only has to keep 50% of the
oil from circulating, which is apparently easy to do,
depending on who you ask. Some say that compressor manufacturers can prevent all of the oil from
circulating, while others say it's difficult to meter
an exact amount.
Estimates from trusted sources put these systems
at about 2-3% of oil circulation overall. There are
a few reasons for this. First, if there was no oil in
circulation, then there would be no way to transport dye around the system. Even if dye were to be
added, it would simply be carried into the compressor by the refrigerant, and then it would stay there
because the oil separator wouldn't let it out.
But technicians and most engineers strongly believe that leak detection dye is an important and
necessary tool for finding leaks in MAC systems.
That's why 2-3% of oil is allowed to remain in circulation with the refrigerant. It's that little bit which
helps the dye to circulate and coat the inside of

A HOT BUTTON ISSUE

Steve Schaeber

Service technicians need to know about and understand these issues, because we're seeing many
more vehicles change over to this style of compressor. If this pattern continues, uncertainty will arise
with techs that are used to seeing larger oil charges,
and when they see the small numbers, they will
think something is wrong with the data, and add
extra oil anyway. See Figure 6.
What then would happen if a technician were to
add, say, an extra half bottle (about 4 ounces). Where
would the extra oil end up? We're not sure. It could
pool up in the evaporator or drier, or it may accumulate in the compressor body itself. After all,
if the job of the oil separator is to keep all but 2 or
3 % in circulation, then it would make sense that it
would keep any extra added oil in the compressor
body.
But how much can the compressor realistically
hold? If for example the entire system is only supposed to have 3 ounces of oil, and only 0.09 ounces
(3%) is in circulation, that means 2.91 ounces are
in the body. But if the technician thinks the specs

Figure 6: Many vehicles from the last 10 years or so are using oil separators, which means greatly reduced oil charge amounts in some systems. Pay close attention if one
of these shows up in your bay. Models from just a few years ago may have required double the amount of oil. Even though the number may not look right, it probably is,
and adding too much oil can be detrimental to the system.

October 2017

MACS Service Reports

Table of Contents for the Digital Edition of MACS Monthly Newsletter - 2017