Guardian 4389 Diagnostic Repair Manual page 45

SECTION 2.4
DIAGNOSTIC TESTS
TEST 13 - CHECK AND ADJUST
VOLTAGE REGULATOR
DISCUSSION:
For additional information, refer to description and
components Page 2.1-3.
PROCEDURE:
With the frequency between 61-62 Hertz, slowly turn the
slotted potentiometer (Figure 12) until line voltage reads
244-252 volts.
NOTE: You must remove the access panel on top of the
control panel to adjust the voltage regulator.
NOTE: The voltage regulator is housed above the
generator control panel. The regulator maintains a
voltage in direct proportion to frequency at a 2-to-1
ratio. For example, at 62 Hertz, line-to-neutral voltage
will be 124 volts.
Figure 12. Voltage Adjustment Potentiometer
RESULTS:
1. If the frequency and voltage are now good, discontinue
tests.
2. If frequency is now good but voltage is high or low, go to
Problem 1, Test 4.
TEST 14 - CHECK VOLTAGE AND
FREQUENCY UNDER LOAD
DISCUSSION:
It is possible for the generator AC output frequency and
voltage to be good at no-load, but they may drop excessively
when electrical loads are applied. This condition, in which
voltage and frequency drop excessively when loads are
applied, can be caused by (a) overloading the generator, (b)
loss of engine power, or (c) a shorted condition in the stator
windings or in one or more connected loads.
Page 2.4-10
PART 2
PROCEDURE:
1. Connect an accurate AC frequency meter and an AC
voltmeter across the stator AC power winding leads.
2. Start the engine, let it stabilize and warm-up.
3. Apply electrical loads to the generator equal to the rated
capacity of the unit.
4. Check the AC frequency and voltage. Frequency should
not drop below approximately 58-59 Hertz. Voltage
should not drop below about 230 volts (plus or minus 2
percent).
RESULTS:
1. If frequency and voltage drop excessively under load, go
to Test 15.
2. If frequency and voltage under load are good,
discontinue tests.
TEST 15 - CHECK FOR OVERLOAD CONDITION
DISCUSSION:
An "overload' condition is one in which the generator rated
wattage/amperage capacity has been exceeded. To test for
an overload condition on an installed unit, the best method is
to use an ammeter. See "Measuring Current" on Page 1.4-2.
PROCEDURE:
Use a clamp-on ammeter to measure load current draw, with
the generator running and all normal electrical loads turned on.
RESULTS:
1. If the unit is overloaded, reduce loads to the unit's rated
capacity.
2. If unit is not overloaded, but rpm and frequency drop
excessively when loads are applied, go to Test 16.
TEST 16 - CHECK ENGINE CONDITION
DISCUSSION:
If engine speed and frequency drop excessively under load, the
engine may be under-powered. An under-powered engine can
be the result of a dirty air cleaner, loss of engine compression,
faulty carburetor settings, incorrect ignition timing, etc.
PROCEDURE:
For engine testing, troubleshooting and repair procedures
refer to Problem 11 on Page 4.3-3. For further engine repair
information refer to the following manuals:
• P/N 0C1103 - Service and Repair Manual for Single
Cylinder GN Engines.
• P/N 0E2081 - Service Manual for GTV-990/760 V-Twin
OHVI Engines.
AC GENERATORS