March 2023 - 22

TOOL BRIEFING
p Figure 2 - Robinair R-134a machine
p Figure 3 - Ecotechnics Dual Gas A/C machine
charge hybrid vehicles. We use Ecotechnics
Dual Gas A/C machine for that (Figure
3). Before purchasing this machine, we
would use Snap-on ACTR4151A refrigerant
gauges, a Matco Tools AC98210A
refrigerant scale, and a virgin tank of
R-134a to charge the hybrid A/C systems.
This ensured that we did not contaminate
these A/C systems. For R-1234yf systems,
we purchased a Robinair AC1234-6 A/C
machine, which has a built-in flushing feature
to ensure that contamination does not
happen (Figure 4).
There are many options for A/C
machines on the market. Do your homework
to see which one is right for you. I
prefer separate machines for each refrigerant.
In the event the machine breaks,
you are not shut down on both refrigerants.
However, if space is a concern, a dual
machine can be quite convenient.
DIAGNOSTICS
When it comes to diagnosing A/C system
performance, most technicians will look at
the system pressures and the vent duct temperature.
I strongly suggest starting with
a full vehicle scan of the car. Remember
that when you push the A/C button, you
are not turning on the A/C directly. You
are asking the vehicle to turn on the air
conditioning. There may be other faults
in the vehicle that are keeping the vehicle
from operating the A/C system.
A complete visual inspection should
be made under the hood. Look for anything
that is out of the ordinary. Check the
engine cooling fan for proper operation and
that there are no restrictions to the airflow
through the condenser. I have run across
vehicles that had accumulated quite a bit of
debris between the radiator and condenser.
This condition caused poor performance
symptoms in the A/C system and higher
than normal system pressures (as the
refrigerant wasn't being cooled enough).
The most effective way to properly diagnose
the operation of the system is to take
temperature measurements at multiple
points through the A/C system's refrigerant
loop. The measurements will be taken
at the inlet and outlet ports of the A/C
components. This can then be considered
to determine the actual cause of the failure.
The main concept of temperature measurement
comes from the fact that refrigerant
temperatures directly correspond to their
pressure. By taking these measurements,
you can see the specific pressure in the
system at each location and not just at the
service ports.
Remember, the key to the air condition22
PTEN MARCH 2023 www.VehicleServicePros.com
ing system is the evaporation and condensing
of the refrigerant. The air conditioning
isn't blowing cold air. It absorbs the heat
energy from the cabin air and transfers it to
the condenser, where the refrigerant then
transfers the heat to the atmosphere.
To learn more about temperature
testing of the A/C system, Jim Cokonis,
an instructor and curriculum developer
for Carquest Technical Institute, wrote
a great article on enthalpy charts. (The
article can be found on PTEN's website,
vehicleservicepros.com/21220569).
p Figure 4 - Robinair R-1234yf machine
http://www.vehicleservicepros.com/21220569 http://www.VehicleServicePros.com
March 2023

Table of Contents for the Digital Edition of March 2023
