TM 5-4310-385-13
SECTION V. UNIT TROUBLESHOOTING
3-13. GENERAL. Troubleshooting at the unit maintenance level requires location of any trouble as quickly as possible.
Once trouble is located, repair or replace the part if authorized to do so or determine if a higher category of maintenance
is required. Repairs by unit maintenance are limited by tools, test equipment and replacement parts allocated to that
level.
3-14. ELECTRICAL SYSTEM.
a.
Problems in the motor control circuitry will usually cause the motor to stop running. Note that there has to be
current through the coil for contacts E1, E2 and E3 to close. This means that the motor won't run if the coil circuit is bad
even though the rest of the circuit is good.
b.
Overload conditions will cause the overload relay contact to open. Overloading may be caused by shorts in the
motor or by a blockage in the compressor. Overload conditions must be removed before the compressor can be put back
in operation. Otherwise, the relay will just open up again.
c.
Once overload conditions have been eliminated, the RESET button on the motor starter box must be pushed to
restart the compressor.
d.
The electric motor is made up of electrical and mechanical components. The main mechanical components
which may fail are the bearings.
e.
Other malfunctions are usually due to problems with the electrical components.
3-15. COMPRESSOR UNIT.
a.
The compressor drive is a fairly simple system. The main problems are improper belt tension, bad alignment and
loose parts.
b.
The intake and exhaust valves are the most critical parts of the compressor. Loss of pumping efficiency can most
often be traced back to the valves.
c.
Problems with not getting enough air are not always caused by the compressor. Leaky fittings or an improperly
adjusted pressure switch may also be at fault.
3-16. TROUBLESHOOTING TABLE. The following columns are used in the Troubleshooting Table.
a.
Malfunction. Malfunctions listed are the ones most likely to happen. Not all possible malfunctions can be
foreseen and listed.
b.
Test or Inspection. Tests or inspections are listed to help you find the cause of the malfunction. The malfunctions
which are most likely to occur are listed first. The malfunctions least likely to occur are listed last.
c.
Corrective Action. Corrective actions are listed to help eliminate the malfunction. Where the corrective action is
too complicated to be listed in full detail, the paragraph number of the maintenance procedure is given in parentheses.
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