March 2022 - 34

TOOL BRIEFING
p Figure 2 - Snap-on PolarTek EEAC334B
dual machine.
p Figure 3 - Leaking
condenser. Small leak
at tank to core.
p Figure 4 - L Foaming evaporator/condenser
coil cleaner.
The second significant difference is that the machines will
not charge a system if it fails a vacuum decay leak test. When
preparing to charge the system, the machine pulls a vacuum
and monitors vacuum decay, the presence of which indicates a
leak. If no leak is detected, the machine performs a partial system
charge. A series of prompts then guide the tech through an
evaporator leak test. The test begins by turning the blower on low
with only the floor vents selected. The leak detector probe is then
inserted into the center floor duct as far as possible. If no leak is
found, the tech hits the appropriate button and will be asked if
an auxiliary evaporator is present; if so, an additional leak test is
performed. Once all leak tests are passed, the machine performs
a full system charge and prints a slip indicating the amount of
refrigerant recovered and charged.
CASE STUDY: GRADUAL LOSS OF A/C
Each shop will experience different types of A/C complaints
and failures depending on their customer demographic and
geographic location. Shops located in hot climates will be
performing service year-round and likely see higher failure
rates of specific components or systems due to the high-stress
environment they operate in, while more northern shops may
experience service of systems that are ignored for all but the
hottest few months of the year. I would categorize system leaks
as the primary repair, followed by compressor failures in my
corner of the country.
This Silverado came in after frustration at needing refrigerant
recharges yearly, sometimes more often. Based on the complaint
and the previous work described by the customer, it was clear
34 PTEN MARCH 2022 www.VehicleServicePros.com
that we were likely looking for a leak. A complete system scan
was performed using a Snap-on Versus Edge while monitoring
vent temperatures in park with the Power Probe Dual Zone Digital
Wireless Thermometer. This gives the tech a chance to feel the
system's cooling capabilities in a relatively static environment,
which can then be compared to operation on the road. No DTCs
were found, and temperature sensor readings corresponded with
a lack of cooling ability.
A glance at the data PID for the pressure sensor on the high
side hose indicated a pressure of 150 psi, about 100 psi lower than
expected at a 90 degrees F ambient temperature. This further
confirmed an undercharged system. Now that I had enough data,
our Snap-on EEAC334B recovery/recycle machine (Figure 2)
was hooked up, and recovery began. The system was found to be
approximately 0.60 lbs undercharged. Before recharging, a vacuum
test was performed and passed. The system was recharged with
R-134a containing UV dye. The Actron 900 refrigerant sniffer was
used to attempt to pinpoint a leak location quickly, but no precise
results were achieved.
After approximately an hour of running, the system was
checked thoroughly with a Mastercool UV light, and the leak was
located in the condenser (Figure 3). The sniffer was then placed
in the location but showed no signs of leakage. This truck was a
perfect example of a leak small enough to be hard to detect but
large enough to cause a severe drop in A/C performance. It was a
quick and straightforward diagnosis that proves no one test fits all
when it comes to leaks, and as such, a passed vacuum test or sniffer
failing to pick up a leak doesn't guarantee that a leak isn't present.
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March 2022

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