Professional_Tool_And_Equipment_News_March_2020 - 31

that even though refrigerants and
many of the controls (inputs and
outputs) have changed, the basic premise of how the system works remains
very similar to the original design; it
removes heat and humidity from within
the vehicle.
With many of these changes, most
specifically changes to the refrigerants
and their operating pressures and capacities, new test and repair equipment is
required to work on newer vehicles.
When I first started working on A/C
systems, the average refrigerant capacity
was around 3.5 lbs or 56 oz. One of the
major changes in A/C systems has been
a reduction in the capacity of the system,
mostly due to a combination of changes
in refrigerant and to improve fuel economy. Many vehicles built today are using
just 16 to 20 oz. in their systems.
The reduction in capacity is significant. When you were working on a system that was as large as 56 oz., 2 to 3 oz.
of over- or under-charge or contamination of air was not really a big problem
and the system would still function fairly well. With today's smaller capacities,
2 to 3 oz. of contamination or over- or
under-charge can be as much as 10 to 15
percent of the system's capacity and will
have a significant impact on the system's
ability to function correctly.
This fact makes an up-to-date recovery/recycle/recharge (RRR) machine
critical to use. The latest model
machines will allow you to completely
evacuate and remove all the moisture
from the system, then precisely measure and install the correct amount
of refrigerant and oil. Older machines
that do not use current technologies
may not be able to measure refrigerant amounts for these smaller systems
accurately enough.
A current model refrigerant identifier is also necessary to ensure the tester is capable of testing for all current
refrigerants and variants available, and
to make sure the vehicle owner has not
contaminated the system with any of
these refrigerants.

t Ranger's AC-134 CoolCharge RRR machine
evacuates and recovers 95 percent of old
refrigerant and recharges vehicle A/C systems
within +/- 0.5 oz. of the desired charge.

CASE STUDY

A/C analyzer tools are available that
can quickly measure temperatures and/
or pressures at various points in order to
quickly and accurately diagnose an A/C
system. Tools such as the Mastercool
A/C System Analyzer use an algorithm
to calculate the effectiveness of the system by measuring refrigerant charge,
superheat, supercool, and temperature
differences within the system, ensuring
an accurate diagnosis of the system.
With almost every vehicle you see
using some type of electronic A/C controls, a scan tool is mandatory to diagnose the system, especially with vehicles
that utilize a CAN bus. With a scan tool,
you can monitor each input and output
the system uses to regulate temperatures
and pressures throughout the vehicle.
A scan tool may also be used to activate
various actuators such as blend doors
within the system and may also be necessary to calibrate these actuators after
a repair.
Last, but certainly not least, is current
information specific to the vehicle, and
updates from your equipment manufacturer. These updates may be relevant if
the equipment manufacturer has made
changes to their software or hardware
to improve their equipment.

www.VehicleServicePros.com

MARCH 2020

Now, we will discuss a vehicle that has
had an ongoing A/C issue for about a
year. This vehicle is a 2010 GMC Sierra
Pickup with an automatic front and
rear climate system. The used vehicle
was purchased about six months ago by
one of our customers, so they had no
real information about any prior issues
with the HVAC system. The issue they
brought it in for was that the A/C would
work fine for about 20 to 30 minutes,
then the air coming through the vents
would change flow to the floor and the
air would get warm.
This sounds like a simple issue with
many potential causes such as an overcharge, blocked airflow to the evaporator, or a cooling fan issue, just to name a
few. We began our diagnostic testing by
confirming the problem. Once the A/C
had been running for about 20 minutes,
the inside air became warm and the air
diverted from coming out the dash vents
to coming out at the floor.
Once we were able to duplicate the
issue, we connected the vehicle to our
refrigerant identifier which indicated
there was a small amount of air contaminating the system, but it did have
R-134a in the system with no other
contaminants. We connected our RRR
machine and performed a service on the
system. Once the service was done, we
drove the vehicle, and it once again had
the same issue.
We returned to the shop where we
observed the A/C compressor to make
sure it was functioning. We also connected the RRR machine again to
recheck pressures. The compressor was
on, but it was not cycling. Pressures were
slightly higher than before, but within
normal operating specifications. We
then connected our Mastercool analyzer
which indicated the system may have a
restriction in the evaporator, which is
what we suspected.

PROFESSIONAL TOOL & EQUIPMENT NEWS

http://www.VehicleServicePros.com

Professional_Tool_And_Equipment_News_March_2020

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