40 Auto Heating & Air Conditioning
Refrigeration and general HVAC system service
requires specialized tools as well as common hand and
air-operated tools. This chapter covers all the specialized
tools and test equipment needed to service modern HVAC
systems. Studying the tools in this chapter and becoming
familiar with their purposes and use will assist you when
the service chapters call for their use. Make a special effort
to understand the types of service literature. Almost no part
of a modern vehicle can be serviced without the proper
service information.
Diagnostic and Test Equipment
The following equipment must be obtained to perform
any refrigeration or other HVAC system diagnosis. This
equipment is also used to perform some HVAC ser vice and
replacement.
Gauge Manifolds
Gauge manifolds are the most basic of all refrig-
eration system tools. The gauge manifold is used as both
a diagnosis and a service tool. The technician must have
R-134a and R-12 manifolds to service modern vehicles. Many
shops with refrigerant service machines also have one or more
gauge manifolds to make pressure checks when the machine
is being used on another vehicle. Manifold gauges are used to
remove contaminated or unknown blend refrigerants from the
air conditioning system, reducing the chance for cross-con-
taminating a service machine. In shops that perform a large
volume of air conditioning work, technicians often have their
own gauge manifolds as part of their toolset.
All gauge manifolds have the same basic parts,
although there are some variations among manufacturers.
The major parts of a common gauge manifold are shown
in Figure 3-1. Refer to this fi gure as you read the following
paragraphs.
Manifold Body and Hand Valves
The manifold body is made of brass or aluminum.
Passages are drilled in the body to connect the other
manifold parts. Some manifold bodies have a sight glass
to observe the fl ow of refrigerant. Hand valves are used
to control the fl ow of refrigerant through the passages of
the manifold body. A cross-section of the manifold body
and hand valves is shown in Figure 3-2. Note the internal
passages are arranged so the gauges can read refrigeration
system pressures when the valves are closed.
The hand valves used on R-12 and R-134a gauge mani-
folds are usually arranged in the same way, or on a slant or
in front of the manifold. These different arrangements make
manifold identifi cation easier. Valve wheels for the high and
low sides are identifi ed by color. The low side handwheel is
made of blue plastic or has a blue decal in its center. The high
side handwheel is made of red plastic or has a red decal.
Figure 3-1. The refrigerant pressure gauge manifold is the universal tool for HVAC service. Gauge
manifolds should be carefully handled to maintain their calibration. (TIF Instruments)
Compound gauge
(low pressure)
Pressure
gauge
Low side
handwheel
Manifold
sight glass
Manifold
body
Hook shaft
High side
handwheel