eventually were just "improbable" and actually had
happened. Remember, new parts are just thatnew. It
does not mean they are good functioning parts.
4. Dont cure the symptom and leave the cause.
Recharging a refrigerant system may correct the
condition of insufficient cooling, but it does not correct
the original problem unless a cause is found. A properly
working system does not lose refrigerant over time.
5. Be sure the cause is found; do not be fooled into
thinking the cause of the problem has been found.
Perform the proper tests; then double-check the results.
The system should have been checked for refrigerant
leaks. If no leaks were found, perform a leak test with
the system under extremely high pressure. If the system
performed properly when new, it had to have a leak to be
low in charge.
6. No matter what form charts may take, they are
simply a way of expressing the relationship between the
basic logic and a physical system of components. It is a
way of determining the cause of a condition in the
shortest possible amount of time. Diagnosis charts
combine many areas of diagnosis into one visual display
that allows you to determine the following:
The probability of certain things occurring in a
The speed of checking certain components, or
functions, before others
The simplicity of performing certain tests before
The elimination of checking huge sections of a
system by performing simple tests
The certainties of narrowing down the search to
a small area before performing in-depth testing
The fastest way to find a condition is to work with
the tools that are available, which means working with
proven diagnosis charts and the proper special tools for
the system being worked on.
S e r v i c i n g p r o c e d u r e s f o r a u t o m o t i v e
air-conditioning units are similar to those used to
service conventional air-conditioning systems.
Discharging, evacuating, charging procedures,
connections, and positions of valves on the gauge
manifold set are shown in figure 7-41.
Servicing procedures for the VIR system are also
similar to those used when servicing conventional
air-conditioning systems. However, the hookup of the
manifold gauge set is to the VIR unit.
high-pressure fitting is located in the VIR inlet line.
The low-pressure fitting is located in the VIR unit.
SYSTEM VISUAL INSPECTION
It is often possible to detect a problem caused by a
careful visual inspection of the air-conditioning
refrigerant system. This includes broken belts,
obstructed condenser air passages, a loose clutch,
loose or broken mounting brackets, disconnected or
broken wires, and refrigerant leaks.
A refrigerant leak usually appears as an oily
residue at the leakage point in the system. The oily
residue soon picks up dust or dirt particles from the
surrounding air and appears greasy. Through time, this
builds up and appears to be heavy, dirt-impregnated
Most common leaks are caused by damaged or
missing O-ring seals at various hose and component
connections. When these O rings are replaced, the new
O rings should be lubricated with refrigerant oil. Care
should be taken to keep lint from shop towels or cloths
from contaminating the internal surfaces of the
connection. Leakage may occur at a spring lock
coupling if the wrong O rings are used at the coupling.
Another type of leak may appear at the internal
Schrader type of air-conditioning charging valve core
in the service gauge port valve fittings. If tightening
the valve core does not stop the leak, it should be
replaced with a new air-conditioning charging valve
Missing service gauge port valve caps can also
cause a refrigerant leak. If this important primary seal
(the valve cap) is missing, dirt enters the area of the
air-conditioning charging valve core. When the
service hose is attached, the valve depressor in the end
of the service hose forces the dirt into the valve seat
area, and it destroys the sealing surface of the
air-conditioning charging valve core. When a service
gauge port valve cap is missing, the protected area of
the air-conditioning charging valve core should be
cleaned and a new service gauge port valve cap should
The service gauge port valve cap must be
installed finger tight. If tightened with
pliers, the sealing surface of the service
gauge port valve may be damaged.