Quietpact 40G Diagnostic Repair Manual Model 4700 - Generac Parts

Section 7
DIAGNOSTIC TESTS
Introduction
The “Diagnostic Tests” in this chapter may be performed
in conjunction with the “Flow Charts” of
Section 6. Test numbers in this chapter correspond to
the numbered tests in the “Flow Charts”.
Tests 1 through 17 are procedures Involving problems
with the generator’s AC output voltage and frequency
(Problems 1 through 4 in the “Flow Charts”).
Tests 18 through 40 are procedures involving problems
with engine operation (Problems 5 through 9 in the
“Troubleshooting Flow Charts”).
You may wish to read Section 4, “Measuring
Electricity”.
NOTE: Test procedures in this Manual are not
necessarily the only acceptable methods for diagnosing
the condition of components and circuits.
All possible methods that might be used for system
diagnosis have not been evaluated. If you
use any diagnostic method other than the method
presented in this Manual, you must ensure
that nether neither your safety nor the product’s
safety will be endangered by the procedure or
method you have selected.
Test 1 – Check No-Load Voltage and
Frequency
DISCUSSION:
The first step in analyzing any problem with the AC
generator is to determine the unit’s AC output voltage
and frequency. Once that has been done, you will
know how to proceed with specific diagnostic tests.
PROCEDURE:
1. Set a volt-ohm-milliammeter (VOM) to read AC voltage. Connect
the meter test leads across customer connection leads T1
(Red) and T2 (White).
2. Disconnect or turn OFF all electrical loads. Initial checks and
adjustments are accomplished at no-load.
3. Start the engine, let it stabilize and warm up.
4. Read the AC voltage.
5. Connect an AC frequency meter across AC output leads T1
(Black) and T2 (White). Repeat the above procedure.
RESULTS:
For units rated 60 Hertz, no-load voltage and frequency
should be approximately 122-126 VAC and 61-63
Hertz respectively.
1. If AC voltage and frequency are BOTH correspondingly high or
low, go to Test 2.
2. If AC frequency is good but low or residual voltage is indicated,
go to Test 3.
3. If AC output voltage and frequency are both “zero”, go to Test 12.
4. If the no-load voltage and frequency are within the stated limits,
go to Test 13.
NOTE: The term “low voltage” refers to any voltage
reading that is lower than the unit’s rated voltage.
The term “residual voltage” refers to the output
voltage supplied as a result of Rotor residual magnetism
(approximately 5-12 VAC).
Test 2 – Check Engine Governor
DISCUSSION:
Rotor operating speed and AC output frequency are
proportional. The generator will deliver a frequency of
60 Hertz at 3600 Rotor rpm or 62 Hertz at 3720
Rotor rpm.
The Voltage Regulator should be adjusted to deliver
120 VAC (line-to-neutral) at a frequency of 60 Hertz or
124 VAC (line-to-neutral at 62 Hertz. It is apparent
that, if governed speed is high or low, AC frequency
and voltage will be correspondingly high or low.
Governed speed at no-load is usually set slightly
above the rated speed of 60 Hertz (to 62 Hertz), to
prevent excessive rpm, frequency and voltage droop
under heavy electrical loading.
Governor Adjustment
1. Loosen the GOVERNOR CLAMP BOLT.
2. Push Spring end of GOVERNOR LEVER clockwise to wide
open throttle position of lever.
a. Hold the GOVERNOR LEVER at wide open
throttle and, with a pair of pliers, rotate the
GOVERNOR SHAFT fully clockwise (CW). Use
a minimum amount of force against the governor
shaft.
b. While holding the GOVERNOR SHAFT fully
clockwise and the GOVERNOR LEVER at wide
open throttle, tighten the GOVERNOR CLAMP
BOLT to 70 inch-pounds (8 N-m).
GOVERNOR
SPRING
GOVERNOR
ADjUST
BRACkET
GOVERNOR
LEVER
TO CARBURETOR
THROTTLE
GOVERNOR
ADjUSTMENT
NUT
Figure 7-1. – Governor Adjustment
Page 36