Test 14 - Check Voltage And Frequency Under Load; Test 15 - Check For An Overload Condition; Test 16 - Check Engine Condition - Generac Power Systems 7 kW NG Repair Manual

AC GENERATORS
Table 15. Stepper Motor Testing
Test Point A Test Point B
Red Orange
Red Yellow
Red Brown
Red Black
Red Ground
Figure 58. Six Pin Connector Wire Colors
Results
1. If the Stepper motor in Step 5 moved to the wide-open
position, the closed position in Step 9, and the VOM
indicated CORRECT resistance values, refer back to flow
chart.
2. If the Stepper motor failed to change the throttle position
in Steps 5 or 9, replace Stepper motor.
3. If the Stepper motor in Step 5 moved to the wide-open
position, the closed position in Step 9, and the VOM
indicated IN-CORRECT resistance values, replace Stepper
motor.
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 performance, or (c) a shorted condition in the stator
windings or in one or more connected loads.
Procedure
1. Set Volt-Ohm-Milliammeter (VOM) to measure AC voltage.
2. Connect an accurate AC frequency meter and an AC
voltmeter across the stator AC power winding leads.
3. Start the engine, let it stabilize and warm-up.
PART 2
Resistance Value
10Ω
10Ω
10Ω
10Ω
INFINITY
BLACK
BROWN
YELLOW
ORANGE
RED
EMPTY
4. Apply electrical loads to the Generator equal to the rated
capacity of the unit. Measure and record the frequency
and the voltage.
Results
1. If the VOM indicated 60 Hz and approximately 248 VAC
during full load, discontinue testing.
2. If the VOM indicated a frequency and voltage that dropped
while under full load, refer back to flow chart.
TEST 15 – CHECK FOR AN 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 recommended
method is to use an ammeter. See Section 1.4 "Measuring
Current."
Procedure
1. Connect the clamp-on ammeter to the Generator
according to the ammeters manufacture specifications.
2. Transfer all normal electrical loads to the Generator,
measure and record the amperage.
Results
1. If the ammeter indicated amperage readings that were
ABOVE the unit's specified ratings, reduce loads to the
units rated capacity.
2. If the ammeter indicated amperage readings that were
BELOW the unit's specified ratings, but RPM and
frequency dropped excessively refer back to flowchart.
TEST 16 – CHECK ENGINE CONDITION
Discussion
If engine speed and frequency drop excessively under load, the
engine may be underpowered. An underpowered engine can
be the result of a dirty air cleaner, loss of engine compression,
faulty fuel settings, or incorrect ignition timing, etc. A decrease
in available horsepower will proportionally lead to a decrease
in kW.
Procedure
For engine testing, troubleshooting, and repair procedures refer
to Section 4.3. For further engine repair information, refer to
the appropriate engine service manuals.
Section 2.4
Diagnostic Tests
Page 57