Section Il. TROUBLESHOOTING
This section contains troubleshooting or malfunc-
tion information and tests for locating and correcting
most of the troubles which may develop in the genera-
tor sets. Each malfunction or trouble symptom for an
individual component, unit, or system is followed by a
list of test or inspections necessary for you to deter-
mine probable causes and suggested corrective actions
for you to remedy the malfunction.
a. This manual cannot list all possible malfunc-
tions that may occur or all tests or inspections, and
corrective actions. If a malfunction is not listed
(except when malfunction and cause are obvious), or is
not corrected by listed corrective actions, you should
notify higher level maintenance.
b. Table 5-2 lists the common malfunctions that
you may find during the operation or maintenance of
the generator sets or their components. You should
perform the tests/inspections and corrective actions in
the order listed.
Before you use this table, be sure you have
performed all normal operational checks. If
you have a malfunction which is not listed
in this table, notify the next higher level of
maintenance. Air force users may perform
maintenance within the scope of their capa-
Table 5-2. TROUBLESHOOTING
TEST OR INSPECTION
ENGINE FAILS TO START OR MALFUNC-
Inspect the engine for an electrical or mechanical
Refer to the appropriate service manual
(See Appendix A).
GENERATOR FAILS TO BUILD UP RATED
Step 1. Manually flash the field as follows:
(1) Connect two 1.5 volt flashlight
batteries in series and connect a wire to
(2) Connect the positive wire from
the batteries to terminal No. 5 on the
(3) Start the generator set.
Table 5-2. TROUBLESHOOTING - Continued
TEST OR INSPECTION
2. GENERATOR FAILS TO BUILD UP RATED
(4) Momentarily touch the negative
wire to terminal No. 6 on the voltage
regulator to flash the field.
If the field cannot be flashed, proceed to
Inspect the voltage regulator for cracks,
signs of overheating and other damage.
Test the voltage regulator as follows:
(1) Voltage Regulator (AC Unit).
(a) Select desired voltage setting
on the voltage changeover switch ( 120 V
or 240 V) and start the generator set.
Load cables should not be attached to
the output terminals.
(b) Using a multimeter, check
voltage across output terminals to verify
reading on set voltmeter. If the votage is
low and adjustment of the variable resis-
tor will not correct the deficiency, check
the exciter voltage across terminals 5 or
6 of the voltage regulator. This voltage
will vary, but should be about 25 volts
DC. If no voltage appears on the regula-
tor terminals, the voltage regulator is
defective and should be replaced.
(c) If voltage across regulator ter-
minals 5 and 6 is satisfactory, stop the
generator set, attach the load cables, and
restart the set.
(2) Voltage Regulator (DC Unit).
(a) Disconnect load cables and
start generator set.
(b) Trip the circuit breaker to
ON position, and observe reading on
(c) Using a multimeter, check the
voltage across the output terminals to
verify the reading on the set voltmeter. If
the voltage is low and adjustment of the
variable resistor will not correct the defi-
ciency, check the exciter voltage across
terminals 5 and 6 of the voltage regula-
tor. This voltage will vary but should be
about 25 volts DC. If no voltage appears
on the regulator terminals the voltage
regulator is defective and should be
Change 8 5-