March 2023 - 20

TOOL BRIEFING
Tools for servicing A/C systems
Modern vehicle air conditioning systems now have several different configurations
and can be damaged if the proper procedures, refrigerants, and oils are not utilized.
By Ross Colket, Contributing Editor
I
t will soon be that time of the
year when we will be breaking
out our A/C machines
regularly to service our client's
vehicles. There are so many
variations on vehicles these
days that when servicing these
systems, you must consult your
service information before working
on a vehicle's A/C system.
When working on hybrid or electrified
vehicles, you will most likely be working
with a three-phase alternating current
A/C compressor that typically runs
on several hundred volts. You will see
your typical high voltage (HV) orange
cabling running to the compressor to let
you know you are working with a highvoltage
system. Yes, those voltage levels
are extremely dangerous, so make sure to
follow manufacturer service directions.
Other concerns for EVs include
the correct compressor oil and even
specific dye for the HV compressors.
If either the wrong oil or dye is used,
they can set HV circuit isolation faults,
shutting the A/C system down. We use
Tracer Products Fluoro-Lite because it
meets manufacturer specifications for
the HV system requirements (having
high dielectric properties). If the wrong
oil is used, most of the manufacturers
do not have any service procedure to
correct the contamination other than
replacing all the system's components.
Keep in mind, for vehicles that the compressor
is driven directly (without a
clutch), you cannot run them without
a refrigerant charge. You risk internally
damaging the compressor.
When working on a modern A/C
system, you must have a professionalgrade
scanner to look at the HVAC system
information. It can give you access to
system pressures, temperatures, flow valves,
and much more. In fact, the modern A/C
systems on many Chrysler vehicles can
take all the system data and self-diagnose.
You will also need the scanner to have
bidirectional controls to operate system
20 PTEN MARCH 2023 www.VehicleServicePros.com
components (such as the flow valves, actuators,
and clutches). One thing to remember
is that the air conditioning system really
is conditioning the air (removing heat and
moisture). An example of this would be a
vehicle in that the A/C system is working
normally, but the air coming out of the
vents is 90 degrees F. Remember that in
the HVAC box, all of the air goes through
the evaporator first, but the air is redirected
through the heater core if warmer cabin
temperatures are desired. If you have a malfunctioning
temperature door or actuator,
it is possible to have 90 degrees F coming
out of the vent, with colder cabin temperatures
desired. Even with a properly operating
A/C system refrigerant loop, since
the air is not being directed away from the
heater core, it will be heated.
REFRIGERANT OILS
We started with mineral oil as a lubricant
in the R-12 systems, and it worked well,
but the problem arose when those systems
were converted to R-134a. The R-134a
refrigerant would not carry the mineral oil
molecules and, therefore, could not lubricate
the compressor.
When doing R-134a retrofits, the
systems were to be flushed and then filled
with either Polyalkkylene Glycol (PAG),
or ester oil, both being synthetic oils. The
problem with both PAG and ester oil is
that they are both hygroscopic, meaning
they will absorb water. If this occurs, the
mixture will create hydrofluoric acid and
damage the internal components of the
A/C system.
Also, keep in mind that it is important
to use the correct weight of PAG oil. There
are three different weights typically used in
the automotive industry (46, 100, and 150).
Where 46 and 100 are the most common,
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March 2023

Table of Contents for the Digital Edition of March 2023
