Guardian 4389 Repair Manual page 99

DC CONTROL
INTRODUCTION
Perform these "Diagnostic Tests" in conjunction with
the "Troubleshooting Flow Charts" of Section 4.3.
The test procedures and methods presented in this
section are not exhaustive. We could not possibly
know of, evaluate and advise the service trade of all
conceivable ways in which testing and trouble diagno-
sis might be performed. We have not undertaken any
such broad evaluation.
TEST 41 - CHECK POSITION OF AUTO-OFF-
MANUAL SWITCH
DISCUSSION:
If the standby system is to operate automatically, the
generator AUTO-OFF-MANUAL switch must be set to
AUTO. That is, the generator will not crank and start
on occurrence of a "Utility" power outage unless that
switch is at AUTO. In addition, the generator will not
exercise every seven (7) days as programmed unless
the switch is at AUTO.
PROCEDURE:
With the AUTO-OFF-MANUAL switch set to AUTO,
test automatic operation. Testing of automatic opera-
tion can be accomplished by turning off the Utility
power supply to the transfer switch. When the utility
power is turned off, the standby generator should
crank and start. Following startup, transfer to the
standby source should occur. Refer to Section 1.8 in
this manual. An "Automatic Operating Sequences
Chart" is provided in Section 1.7. Use the chart as a
guide in evaluating automatic operation.
Following generator startup and transfer to the stand-
by source, turn ON the utility power supply to the
transfer switch. Retransfer back to the "Utility" source
should occur. After an "engine cooldown timer" has
timed out, generator shutdown should occur.
RESULTS:
1. If normal automatic operation is obtained, discontinue
tests.
2. If engine does NOT crank when utility power is turned
off, proceed to Test 42.
3. If engine cranks but won't start, go to Problem 10 in
Section 4.3.
4. If engine cranks and starts, but transfer to "Standby"
does NOT occur, go to Problem 5 in Section 3.3.
5. If transfer to "Standby" occurs, but retransfer back to
"Utility" does NOT occur when utility source voltage is
restored, go to Problem 6 in Section 3.3.
TEST 42 - TRY A MANUAL START
DISCUSSION:
The first step in troubleshooting for an "engine won't
PART 4
crank" condition is to determine if the problem is
peculiar to automatic operations only or if the engine
won't crank manually either.
PROCEDURE:
1. On the generator panel, set the AUTO-OFF-MANUAL
switch to OFF.
2. Set the generator main line circuit breaker to its OFF or
(or open) position.
3. Set the generator AUTO-OFF-MANUAL switch to MANUAL.
a. The engine should crank cyclically through it's
"crank-rest" cycles until it starts.
b. Let the engine stabilize and warm up for a few
minutes after it starts.
RESULTS:
1. If the engine cranks manually but does NOT crank auto-
matically, go to Test 43.
2. If the engine does NOT crank manually, proceed to
Problem 9 in the "Troubleshooting Flow Charts".
TEST 43- TEST AUTO-OFF-MANUAL SWITCH
DISCUSSION:
When the AUTO-OFF-MANUAL switch is set to
AUTO position, battery voltage (12 volts DC) is deliv-
ered to the circuit board via Wire 15A, the closed
switch terminal, Wire 15A, and Pin 10 of the circuit
board connector. This voltage is needed to operate
the circuit board.
Setting the switch to its "Manual" position delivers bat-
tery voltage to the circuit board for its operation. In
addition, when the switch is set to "Manual", 12 volts
DC is supplied to the circuit board via Pin 11 of the
board, Wire 239, the closed switch contacts, Wire 17
and Pin 9 of the circuit board connector.
A. Set to "Auto"
6
183*
5
239
4
178*/17
15A
3
15
2 1
15A
Figure 1. Schematic of AUTO-OFF-MANUAL Switch
PROCEDURE:
Disconnect all wires from switch terminals, to prevent
interaction. Then, use a volt-ohm-milliammeter (VOM)
to test for continuity across switch terminals as shown
in the following chart. Reconnect all wires and verify
correct positions when finished.
SECTION 4.4
DIAGNOSTIC TESTS
B. Set to "Manual"
6
183*
5
239
4
178*/17
15A
3
15
2 1
15A
* IF EQUIPPED
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