Professional Distributor - 28

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DIAGNOSTIC TECH

Diagnostic Corner -
Climate Control Systems
The evolution of thermal management.

odern vehicle refrigeration systems have
advanced tremendously in both design
and efficiency over the years. When I
began working on vehicles in the early '80s, it
BY SCOTT BROWN wasn't uncommon to see vehicles that took 4-5
Scott Brown is an ASE Master Certi- lbs of refrigerant. If the system lost a pound or so,
fied L1 Technician and has over 37
drivers likely wouldn't notice. Charge levels today
years of professional service industry experience. He is an independent typically run less than 2 lbs. A 1/4-lb loss of refrigshop owner in Southern California erant could result in a significant performance
and is engaged at various levels
drop. In the past, refrigeration systems were used
within our complex industry. He has
a deep understanding of the chal- primarily to keep drivers and passengers cool.
lenges technicians experience at the
However, there are other vehicle systems
service level and is continuously
requiring support from the refrigeration system.
striving to move the industry forward
through education and networking. For instance, vehicles equipped with electric drive
Brown founded Diagnostic Network systems may have components requiring thermal
(diag.net) after 22 years of service
management. This may include battery packs, onat iATN, where he retired as
company president in 2018. board chargers, and other power electronics. In this
article, we'll cover air conditioning system operation,
diagnostics, and tooling. We'll also tackle some of the
challenges that DIY refrigeration recharge service
kits can introduce.

REFRIGERATION BASICS
A refrigeration system's primary goal is to move
heat. This is primarily accomplished by pumping
refrigerant carefully through a thermodynamic loop.
The compressor provides the push-pull operation,
and has energy costs to be considered. A great deal
of R&D has resulted in significant compressor
design changes.
Modern compressors no longer featuring a
compressor clutch will have an electronic variable
output control system to regulate the compressor
displacement. This can create diagnostic challenges
for technicians. Later, we'll cover the use of tools to
help with diagnostics.

REFRIGERATION SYSTEM SERVICE
I've seen some electrified vehicles call for desiccant replacement at specific intervals. HVAC systems have always included a receiver filter-drier
component that contains desiccant, which is used
to absorb moisture. Excess moisture will eventually
lead to lower efficiency and compressor failures since
28 Professional Distributor I February 2021 I VehicleServicePros.com

Fig 1 - Desiccant bag and filter

it can negatively affect refrigerant oil's lubrication
properties. A good best practice is to replace the
receiver drier whenever the system is opened.
In regions that place high demand on the A/C
system, frequent drier service may be recommended.
For some vehicles, receiver drier service is straightforward. However, others will require condenser
replacement if the receiver filter drier is integrated.
In other cases, condenser removal may be required
to access it. Figure 1 shows the desiccant bag and
filter assembly removed from a vehicle with a serviceable filter.

INSPECTIONS
One way you can help customers' vehicles maintain
healthy HVAC functionality is to implement inspection and maintenance programs. There are several
tools on the market that can help you perform a
professional inspection.

Cabin air filters

Cabin air filters are easily overlooked, as they're
stored out of sight. Some vehicles may not even
have one, but can be upfitted. According to the
Bosch Automotive Handbook, cabin air filters
have a recommended replacement interval of every
12 months. Take a look at the owner's manuals on
vehicles you service for more info. If you're in an
area where the vehicle may have been subjected

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