Guardian 4389 Repair Manual page 37

AC GENERATORS
INTRODUCTION
This section is provided to familiarize the service
technician with acceptable procedures for the testing
and evaluation of various problems that could be
encountered on prepackaged standby generators with
air-cooled engine. Use this section of the manual in
conjunction with Section 2.3, "Troubleshooting Flow
Charts". The numbered tests in this section corre-
spond with those of Section 2.3.
Test procedures in this section do not require the use
of specialized test equipment, meters or tools. Most
tests can be performed with an inexpensive volt-ohm-
milliammeter (VOM). An AC frequency meter is
required, where frequency readings must be taken. A
clamp-on ammeter may be used to measure AC
loads on the generator.
Testing and troubleshooting methods covered in this
section are not exhaustive. We have not attempted to
discuss, evaluate and advise the home standby ser-
vice trade of all conceivable ways in which service
and trouble diagnosis might be performed. We have
not undertaken any such broad evaluation.
Accordingly, anyone who uses a test method not rec-
ommended herein must first satisfy himself that the
procedure or method he has selected will jeopardize
neither his nor the product's safety.
SAFETY
Service personnel who work on this equipment must
be made 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 be ignited by the slight-
est spark. Engine exhaust gases contain deadly car-
bon monoxide gas that can cause unconsciousness
or even death. Contact with moving parts can cause
serious injury. The list of hazards is seemingly end-
less.
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 don't understand a component, device
or system, do not work on it.
TEST 1- CHECK MAIN CIRCUIT BREAKER
DISCUSSION:
Often the most obvious cause of a problem is over-
looked. If the generator main line circuit breaker is set
to OFF or "Open", no electrical power will be supplied
to electrical loads. If loads are not receiving power,
perhaps the main circuit breaker is open or has failed.
PROCEDURE:
The generator main circuit breaker is located on the
control panel. If loads are not receiving power, make
sure the breaker is set to "On" or "Closed".
If you suspect the breaker may have failed, it can be
tested as follows (see Figure 1):
PART 2
1. Set a volt-ohm-milliammeter (VOM) to its "R x 1" scale
and zero the meter.
2. With the generator shut down, disconnect all wires from
the main circuit breaker terminals, to prevent interaction.
3. With the generator shut down, connect one VOM test
probe to the Wire 11 terminal of the breaker and the
other test probe to the Wire E1 terminal.
4. Set the breaker to its "On" or "Closed" position. The
VOM should read CONTINUITY.
5. Set the breaker to its OFF or "Open" position and the
VOM should indicate INFINITY.
6. Repeat Steps 4 and 5 with the VOM test probes con-
nected across the breaker's Wire 44 terminal and the
E2 terminal.
RESULTS:
1. If the circuit breaker tests good, go on to Test 2.
2. If the breaker tests bad, it should be replaced.
E1 TERMINAL
Figure 1. Generator Main Circuit Breaker Test Points
TEST 2- CHECK AC OUTPUT VOLTAGE
DISCUSSION:
A volt-ohm-milliammeter (VOM) may be used to
check the generator output voltage. Output voltage
may be checked at the unit's main circuit breaker ter-
minals. Refer to the unit's DATA PLATE for rated line-
to-line and line-to-neutral voltages.
SECTION 2.4
DIAGNOSTIC TESTS
E2 TERMINAL
OFF
WIRE 11
TERMINAL
WIRE 44
TERMINAL
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