Professional_Tool_And_Equipment_News_February_2021 - 40

Diagnostic Corner -
Climate Control Systems
The evolution of thermal management.
By Scott Brown, Technical Editor

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 wasn't uncommon to
see vehicles that took 4-5 lbs
of refrigerant. If the system
lost a pound or so, drivers likely
wouldn't notice. Charge levels
today typically run less than 2
lbs. A 1/4-lb loss of refrigerant could result in a significant
performance drop. In the past,
refrigeration systems were used
primarily to keep drivers and
passengers cool.
However, there are other vehicle systems requiring support from the refrigeration system. For instance, vehicles
equipped with electric drive systems may
have components requiring thermal management. This may include battery packs,
on-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 pushpull operation, and has energy costs
to be considered. A great deal of R&D

PTEN

FEBRUARY 2021

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 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

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Fig 1 - Desiccant bag and filter

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

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