Section I. GENERAL INFORMATION
Direct support maintenance includes the repair and replacement of major components/assemblies which are
beyond the scope of unit level repair and which can be accomplished normally within 36 hours and in
SPECIAL TOOLS, TMDE, AND SUPPORT EQUIPMENT.
Refer to Appendix B, Section III, Tools and Test Equipment Requirements, for additional tool and equipment
Repair parts are listed and illustrated in the Repair Parts and Special Tools List Manual (TM 10-5410-228-
24P) for unit, direct support and general support maintenance for the CBPS.
Section II. DIRECT SUPPORT TROUBLESHOOTING PROCEDURES
This section lists common equipment malfunctions and contains instructions to allow maintenance
personnel to diagnose and correct each malfunction. Perform the indicated steps in the order listed. This
section does not list all possible malfunctions. If a malfunction is either not listed or cannot be corrected by
the prescribed procedure, notify support maintenance personnel.
The following identifies general air conditioning malfunctions which may occur. Although typical of the
components which may fail or conditions which effect operation, the ultimate result will be that there will be
no air conditioning, or air conditioning will be insufficient or intermittent.
Always put in a new filter/drier any time an air conditioner system component is removed for
High Suction Line Pressure
By Low Superheat.
Problem lies with thermal expansion valve (figure 3-1). Typical thermal expansion valve problems are as
a. Thermal Expansion Valve Out of Adjustment. If the expansion valve is set for too low a superheat
(gas temperature above the saturation pressure point), too much liquid will be passed into the
evaporator. The suction line will be abnormally cold and liquid may `slug' (flow) back to the
compressor. If the expansion valve is set for too high a superheat, too little liquid will be passed to
the evaporator and the suction line will be abnormally warm.
b. Thermal Expansion Valve Stuck in Open Position. If the thermal expansion valve is stuck in open
position, there will be an excessively low superheat and a possible liquid flow into the compressor.
c. Thermal Expansion Valve is Obstructed. Foreign material may obstruct the thermal expansion valve
port. If the obstruction is small, the resulting operation will be an oscillating condition which will
cause a suction pressure variation of possibly 10 to 15 psi (shown on a pressure test gage on the
suction side). If the obstruction holds the valve open, liquid will flow back to the compressor. This
can cause a liquid lock of the compressor, and may damage the compressor on start-up.