Section 4.5 - Diagnostic Tests; Introduction; Safety; Engine/Dc Troubleshooting - Generac Power Systems 7 kW NG Repair Manual

ENGINE/DC CONTROL

INTRODUCTION

This section familiarizes the service technician with acceptable
procedures for the testing and evaluation of various problems
that can occur on the standby generators with air-cooled
engines. Use this section in conjunction with Section 4.4,
"Troubleshooting Flow Charts." The numbered tests in this
section correspond with those of Section 4.4.
Some test procedures in this section may require the use of
specialized test equipment, meters or tools. Most tests can
be performed with an inexpensive volt-ohm-meter (VOM). An
AC frequency meter is required where frequency readings must
be taken.
Testing and troubleshooting methods covered in this section
are not exhaustive. No attempt has been made to discuss,
evaluate and advise the home standby service trade of all
conceivable ways in which service and trouble diagnosis must
be performed. Accordingly, anyone who uses a test method
not recommended herein must first satisfy himself that the
procedure or method he has selected will jeopardize neither his
nor the products safety.
Figure 107 shows the Volt-Ohm-Milliammeter (VOM) in two
different states. The left VOM indicates an OPEN circuit or
INFINITY. The right VOM indicates a dead short or CONTINUITY.
Throughout the troubleshooting, refer back to Figure 107 as
needed to understand what the meter is indicating about the
particular circuit that was tested.
Note: CONTINUITY is equal to .01 ohms of resistance or a
dead short.
OPEN LINE "INFINITY"
OL
Figure 107.

SAFETY

Service personnel who work on this equipment should be
aware of the dangers of such equipment. Extremely high and
dangerous voltages are present that can kill or cause serious
injury. Gaseous fuels are highly explosive and can ignite by the
slightest spark. Engine exhaust gases contain deadly carbon
monoxide gas that can cause unconsciousness or even death.
Contact with moving parts can cause serious injury. The list of
hazards is seemingly endless.
PART 4
SHORT "CONTINUITY"
.01
When working on this equipment, use common sense and
remain alert at all times. Never work on this equipment while
you are physically or mentally fatigued. If you do not understand
a component, device or system, do not work on it.

ENGINE/DC TROUBLESHOOTING

It is always good practice to continue to ask questions during
the troubleshooting process. When evaluating the problem
asking some of these questions may help identify the problem
quicker.
• What is the generator doing?
• What is the fault that the generator is shutting down for?
• After the fault occurred, what was the LCD displaying?
• Is there another Alarm in the log just previous to the
shutdown?
• Is the fault causing the shutdown a symptom of another
problem?
• Does the generator have the same fault consistently, and
when does it occur?
• What was the generator supposed to do?
• Who is controlling it?
• Exactly what is occurring?
• When is it happening?
• Why would this happen?
• How would this happen?
• What type of test will either prove or disprove the cause of
the fault?
TEST 40 – CHECK POSITION OF AUTO-OFF-
MANUAL SWITCH
Discussion
If the system is to operate automatically, the generator AUTO-
OFF-MANUAL switch must be set to the AUTO position. The
Generator will not crank and start on occurrence of a Utility
failure unless the switch is in the AUTO position. In addition,
the Generator will not exercise every seven (7) days as
programmed unless the switch is in AUTO.
Procedure
With the AUTO-OFF-MANUAL switch set to the AUTO position,
test automatic operation. Testing of automatic operation can
be accomplished by turning off the Utility power supply to
the transfer switch. When the Utility power is turned off the
Generator should crank and start. Following startup, transfer to
the "Standby" position should occur. Refer to Section 1.7.
Results
1. If normal automatic operation is obtained, discontinue
tests.
2. If the engine does not crank when Utility power is turned
off refer back to the flow chart.
Section 4.5
Diagnostic Tests
Page 115