MACS Monthly Newsletter - 2021 - OCT6

or 2021 Blazer, Equinox or GMC Terrain in specific VIN ranges
and the A/C is slow to cool down, compared to " like vehicles. "
Or the car is in for another repair that requires evacuating the
A/C refrigerant, the most common reason an independent
garage might see the vehicle.
GM's bulletin goes on to say the system should be evacuated
into a contaminated refrigerant recovery machine, which
is engineered to meet SAE J2851. If you're not familiar with
this SAE standard, it's really been around for a while and was
originally developed for R-134a. The design of the recoveryonly
machine covers the issue of flammability, of course, because
there are refrigerants on the market that are not approved
for automotive
A/C use, typically hydrocarbon
based.
But the GM bulletin
Figure 7: Signs of refrigerant contamination,
including coating of
trace dye, in GM vehicle A/C
joint.
does not raise this issue.
It's rather cryptic in that
regard. It's directed at
the GM dealer technicians
(as are really all OE
service bulletins). It tells
the technician to remove
the compressor solenoid
and to disconnect the
A/C lines at the compressor,
the condenser
and the expansion valve,
take photos of the joints.
Then the technician is supposed to send the photos in to
GM HVAC engineering and wait for GM to call with further
instructions.
What appears to have happened is this: in the process of
preparing bulk storage of R-1234yf for assembly line use, the
bulk refrigerant was contaminated with a cleaning agent that
contained peroxide, which reacts with the refrigerant. Before
bulk storage facilities and lines are filled with R-1234yf, they're
supposed to be clean and moisture removed by blowing
through with dry nitrogen. If
there's a misstep in the process,
the refrigerant is contaminated.
In the GM bulletin,
the joints show some
green deposits (apparently
from trace dye), some black
deposits and some white
deposits (apparently polymerization
from the reaction
with the peroxide). See Figures
7, 8.
Well, wouldn't a refrigerant
identifier indicate this
issue? No, because the
cleaning agent isn't a type
of refrigerant which an identifier
is designed to detect.
So, what to do next? If there
are none of the deposits (everything
is nice and clean),
the system can be serviced as indicated. But if the vehicle is
within the VIN range of the bulletin, the best approach is to
take no chances and send the car to the dealer.
The lesson to be learned: don't use cleaning agents conFigure
8: In addition to
debris, GM compressor
solenoid contamination
includes white deposits
from peroxide reaction.
taining peroxide. Also be wary of thread locking compounds
for the joints, as some of these may contain peroxide. And
whenever you open a system, be sure to evacuate it properly
to prevent admission of air, which as you know, causes performance
problems of its own. v
Cause Of A/C Failure We Often Forget
Sure, damage to vehicle wiring is a common issue, but
there's one root cause that's increasing in frequency that we
often forget, and the A/C system is a common target. It's wiring
that's been chewed on by rodents. Typically, it has occurred
in areas where rodents are more prevalent, but now
there's a factor that results in attracting them - both warmth
and food. Certainly, there are parts of the car that retain
warmth in cold weather, and if there's a way for a rodent to
get in, it will. But even if you don't have a half-eaten slice of
pizza left out, there's something almost as tasty that the car
manufacturer installed: car wiring, and the HVAC wiring has
become a particular target. Late-model car wiring typically
has insulation made from soy, replacing the petroleum-based
insulation that long has been used. Soy insulation is not only
cheaper, but it's been considered more environmentally
friendly because of its non-fossil-fuel composition. See Figure
9. Soy may be used in both the colored plastic insulation
on the wiring and in the black corrugated harness housing.
It's probably not the only cause of rodent infestation, but has
certainly contributed to the increase so widely seen.
October 2021
6
Rodent damage to wiring is not covered by the car warranty,
but may be (to some extent) by a car insurance policy.
As a " close the barn door after the horse has escaped " type
of preventive approach after a repair, you can recommend
the following: 1) naturally it's preferable to park indoors. (2)
keep the windows and sunroof fully closed. (3) apply a rodent
repellent. Honda dealers sell a roll of tape impregnated with
capsaicin, a human pain reliever that has been found to also
Figure 9: Wiring damage from rodent infestation.
MACS Service Reports
acdelcotds.com
Steve Schaeber
acdelcotds.com
http://www.acdelcotds.com http://www.acdelcotds.com
MACS Monthly Newsletter - 2021

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