TRUCK SERVICE MANUAL
BODIES AND CABS
COMPONENT PROBLEM ANALYSIS
Some possible failings of the compressor include:
Leaking Front Seal This allows refrigerant and
lubricating oil to escape from system in loss of
cooling and damage to compressor.
Bearing Failure Usually the result of material wear
but can result from excessive drive belt tension or
Burned-Up Compressor Caused by lack of lubricating
oil. This emphasizes the need for checking the oil
level in the compressor at the time of system service.
In the event that compressor failure is severe enough
to form metal particles, purge compressor discharge-
to-filter-dehydrator lines with 4.5 kg (1 lb.) of
refrigerant and replace the filter-dehydrator.
For compressor service procedures, refer to Bodies
and Cabs, Section CTS-2577 of the Truck Service
The two most common clutch failures are:
Broken Torque Springs.
Both of these failings are usually symptomatic of
troubles somewhere else in the system. (Example: A
restriction in the condenser will cause excessive head
pressures, which in turn will overwork the compressor and
clutch, eventually causing failure of one or both.)
For clutch service procedures, refer to Bodies and
Cabs, Section CTS-2577 of the Truck Service Manual.
THERMOSTATIC TEMPERATURE CONTROL SWITCH
The thermostatic temperature control switch is
relatively trouble free; however, should it fail, it must be
replaced. If the clutch remains engaged continually, check
the sensing tube of the control switch to see that it has not
been pulled out of the evaporator core. The sensing tube
should be located in the evaporator core as shown in Figure
Also, make sure air conditioning (A/C) control cable
is properly adjusted.
Possible problems with the condenser include:
A leak in the condenser.
A stoppage or restriction of refrigerant flow through
the condenser. This could result from some foreign
material inside the core or by a sharp bend or dent in
the condenser tubing or in the hoses leading into or
out of the condenser.
(Make a visual check to make sure this has not
A restriction of air flow through the condenser. This
is the most common problem and results from dirt,
leaves, etc. collecting on the front area.
A stoppage or restriction of refrigerant flow or air flow
through the condenser will be indicated by a high
discharge pressure reading on the test gauge.
Restriction of refrigerant flow will show a lower than
Restricted air flow will build high discharge and
In some instances tubing may be replaced or leaks
may be repaired by silver soldering if the spot is
accessible, however, a stopped-up or internally
restricted core must be replaced.
Never weld, solder, steam clean or use any excessive amount
of heat on any of the refrigerant lines or components of the
refrigeration system while the system is charged. Heat
applied to any part would cause-the pressure of the refrigerant
within the closed system to become excessive.
Possible problems at the expansion valve include:
Stoppage - Stoppage in the system tends to occur at
the valve or at the filter-dehydrator tank.
Valve Sticking - The valve tends to stick closed
cutting off the refrigerant supply to the evaporator
and stopping all cooling from the air conditioner.