244 Auto Heating & Air Conditioning
Step 5—Recheck the Cause of the
Problem
In this step, the cause of the problem determined in
Step 4 is rechecked. This step requires reviewing the various
test procedures performed in the last step, and determining
whether the suspect component is likely to be the source of
the problem. It is often helpful to take a short break to con-
sider all possible causes and determine if what you have
found is the most likely cause of the problem or the only
thing that could be defective. Review how the particular
system works, and how the defect could cause the system
problem.
Before going to the next step, recheck the condition of
the suspect part as much as possible. Also recheck all other
related parts. This will ensure you have not condemned the
wrong part or overlooked another defect. For instance, if
one O-ring is leaking, do not assume it is the only defective
seal. Thoroughly check the rest of the refrigeration system
for leaks.
Always Perform Additional Tests
Additional testing is especially important when the
suspected part is a solid-state or an otherwise untestable
device, such as an automatic temperature control assem-
bly. Such parts are too expensive to simply replace without
knowing for sure whether they are good or bad. Making
further checks to confi rm the problem is always a good
idea, if only to increase your confi dence about fi nding the
defective part. Not many technicians are sorry they made
further checks, but a lot of them are sorry they did not.
Deciding on Needed Work
Deciding on needed work is a process of interpreting
the results of all diagnostic tests. It is simply a matter of
taking all test readings and deciding what they mean. As
discussed earlier, the test results can be simple observations
of visible defects, detailed readings from elaborate test
equipment, or any procedure in between.
Before condemning any part based on test results,
mentally review its interaction within the system and
with the various engine and vehicle systems. Then decide
whether the part in question can cause the particular test
reading or symptom. For instance, if the HVAC system is
losing refrigerant and you have located a leak at the evapo-
rator, do not assume it is the only source of leaks. Check the
entire system thoroughly before giving an estimate.
Troubleshooting charts and other diagnostic informa-
tion can be a great asset to this process, Figure 15-24. If
researched and prepared correctly, the troubleshooting
chart will list all the possible causes of the problem, allow-
ing you to check everything in a logical sequence. Properly
used, such information will speed up the checking and
isolating process.
Deciding on the Proper Repair Steps to Take
The amount and type of corrective action must also
be determined. In some cases, the repair is as simple
as reattaching a vacuum hose, removing grease, dirt, or
debris from a sensor connection, or tightening a belt.
In other cases, major unserviceable parts, such as the
evaporator or condenser, must be replaced to correct
the problem. To reduce the possibility of future prob-
lems, you should also service parts that interact with the
defective part. An example is replacing a fi xed orifi ce
tube when the compressor is replaced. In all cases, the
technician must thoroughly determine the extent of the
repairs before proceeding.
Factors that must be considered when deciding to
adjust, rebuild, or replace a part are ease of adjustment, the
need for special tools, cost of the replacement part, and the
possibility the old part will fail again.
If a part is easily adjustable, you can try the adjustment
procedure before rebuilding or replacing. Generally, most
HVAC parts cannot be adjusted. If adjusting the part does
not restore its original performance, the part can still be
rebuilt or replaced with little time lost. If there is any doubt
about whether an adjustment has corrected a problem,
replace the part.
Rebuild or Replace?
In cases when a defective component can be rebuilt,
the investment in materials and time must be weighed
against the possibility that rebuilding the part may not fi x
the problem. It is often cheaper to install a new part than
to spend time rebuilding the old one. Many repair shops,
and even some new vehicle manufacturers, are going
increasingly to a policy of replacing complete assemblies.
You must determine if rebuilding is cost effective. However,
keep in mind that most HVAC parts cannot be rebuilt. Parts
that can be rebuilt include the compressor, radiator, and
water pump.
In many cases, the customer will come out ahead
with a new or remanufactured assembly instead of
paying to rebuild an old part. The price of the new
or remanufactured part is often less than the charge
to rebuild the old part. These parts often come with
a limited warranty from the remanufacturer and the
assurance the part was assembled in a clean, controlled
environment. The technician will often come out ahead,
since the labor time saved rebuilding the old part can
be devoted to other work.
Along with the cost of repairs, another factor that must
be considered is the necessity to retrofi t the vehicle to use
another refrigerant. The cost of retrofi tting will have to be
included, especially if the parts being replaced are not
normally serviced during a retrofi t.
Therefore, when deciding what to do to correct a
problem, make sure that all parts that could contribute
to the problem have been tested. In one form or another,
every possible component and system should be tested.
Then you can decide with assurance what components
are defective.