Chapter 15 Refrigeration System Diagnosis and Leak Detection 233
❑
Radiator fan. Check for bent or missing blades and
loose attaching bolts. If the fan is electric, make sure
the motor works properly.
❑
Fan clutch (when used). If the center of the fan clutch
is leaking oil, the front of the clutch will be oily.
Look for other obvious problems such as loose or missing
compressor mounting bolts, loose electrical wires, dented or
damaged system components, and missing shrouds around
the condenser and radiator. Check vacuum hoses to ensure
they are not cracked, misrouted, or disconnected.
Check the vehicle dashboard for damaged HVAC
controls. Operate the dashboard controls and ensure they
are working. Look for levers that are stuck or do not appear
to be connected, sticking pushbuttons or knobs, or hissing
noises when certain modes are selected. Turn the ignition
key to the on position and check if the blower operates on
all speeds, and if any indicator screens or other electrical
indicators are working.
If the problem appears to be electrical or electronic,
you may want to visually check the fuses, related electri-
cal connections, and grounds. In many cases, these simple
checks will uncover the problem, or give you a likely place
to start in Step 3.
Refrigerant Identifi cation
Check the refrigerant type to determine whether it
agrees with the manufacturer’s label or retrofi t label. Even
if the label and fi ttings indicate the system has not been
retrofi tted, it is a very good idea to check the refrigerant
composition. Figure 15-6 shows a refrigerant identifi er
being used to check an air conditioner. The type of refriger-
ant should match the retrofi t label (if present) and the type
of service ports. A good refrigerant identifi er will also check
for unknown refrigerants, R-22 blends, and for contamina-
tion by unknown gases.
Caution: Do not attach a refrigerant service
center to a system until you can verify the
composition of the refrigerant. If the refrig-
erant is OK, you can attach a refrigerant recovery/re-
cycling service center. If the refrigerant is contaminated
or you cannot verify its composition, use a set of mani-
fold gauges to initially check the system charge.
Diagnosing Odor Complaint
Because of the dampness and cool conditions, the
evaporator and blower case create an environment for the
growth of mold and mildew. This problem is usually seen in
areas with hot humid climates. Mold and mildew will cause
the air coming out of the vents to have a musty smell. In most
cases, the problem will disappear over time as climate con-
ditions change. However, in some cases, the problem may
persist due to leaves or other debris in the evaporator case or
microbial growth on the evaporator core face. In these cases,
the evaporator and case needs to be disinfected. If debris is
present in the case, it must be removed or else the problem
will return in a short period of time.
If the customer complains the windows frequently
fog up coupled with the smell of coolant, a leaking heater
core may be the cause. A massive refrigerant leak from the
evaporator could cause refrigerant oil to be sprayed in the
blower case, giving the air an oily smell. There are many
other causes of blower case odors, ranging from malfunc-
tioning electrical components to dead vermin in the case.
Step 3—Determine Which System Is
Causing the Problem
The third step is to determine which HVAC system
components or vehicle systems could cause the problem.
The fi rst reaction to what appears to be a refrigeration prob-
lem is to decide whether or not the refrigeration system is
defective. However, the refrigeration system is composed
of mechanical and electrical parts and interacts with other
vehicle systems. To determine the source of the problem,
you must combine the information you obtained in Steps 1
and 2 with the knowledge you obtain by making a system
performance test as part of this step.
Instead of looking for something obviously wrong, as
you did in Step 2, you are using the performance test to
check for something that could cause the specifi c problem.
This will also help you to eliminate things that could not
cause the problem, so in Step 4 you can concentrate on any
suspected components.
Functional and Performance Tests
The following is a general system function and per-
formance test. A functional test checks for proper system
operation at different settings. The performance test
checks the refrigeration and heating system components
Figure 15-6. Before performing any service to the refrigera-
tion system, always identify the refrigerant. This may save you
a lot of trouble later. This refrigerant identifi er will identify the
refrigerant as R-134a, R-12, or as unknown. It will also give the
percentages of R-134a, R-12, and unknown components.