Guardian 4721, Repair Manual

Page: 87 / 115

DC CONTROL
LIQUID COOLED
ENGINE UNITS
SECTION 4.4
DIAGNOSTIC TESTS
PART 4
Page 83
CONNECT
ACROSS
SWITCH METER
TERMINALS POSITION READING
1 and 2 AUTO Continuity
MANUAL Infinity
OFF Infinity
1 and 3 AUTO Infinity
MANUAL Continuity
OFF Infinity
4 and 5 AUTO Continuity
MANUAL Infinity
OFF Infinity
4 and 6 AUTO Infinity
MANUAL Continuity
OFF Infinity
RESULTS:
1. Replace switch is defective.
2. If switch is good, go to Test 4.
Figure 2. AUTO-OFF-MANUAL Switch Test Points
Figure 3. AUTO-OFF-MANUAL Switch Wiring
TEST 4 - INSPECT AUTO-OFF-MANUAL
SWITCH TO CONTROL BOARD WIRING
DISCUSSION:
Any open or disconnected wiring between the switch
and the control board, or between the switch and
other components, can have the same effect as an
open or defective switch. See Figure 3.
PROCEDURE:
Inspect and test all wires connected to the switch ter-
minals for open, disconnected or shorted condition.
This includes (a) Jumper Wire 15A between Switch
Terminals 5 and 6; (b) Wire 15 between Terminal 4
and the circuit board; (c) Wire 15A between switch
and circuit board; (d) Wire 183 between Terminal 2
and TB3; (e) Wire 239 between Terminal 1 and the
circuit board; Wire 178 between Terminal 3 and TB3;
(f) Wire 178 between Terminal 3 and the circuit board.
RESULTS:
Repair, reconnect or replace any bad wiring.
TEST 5 - CHECK 15 AMP FUSE (F1)
DISCUSSION:
A blown fuse F1 will open the DC power supply to the
AUTO-OFF-MANUAL switch and to the control board.
This will render the circuit board incapable of cranking
or starting the engine, since its power supply is gone.
PROCEDURE:
Push in on fuse holder cap and turn counterclockwise
to remove cap and fuse. Check the fuse with a VOM
for open condition indicating that fuse is blown.
RESULTS:
1. Replace fuse if blown.
2. If fuse is good but engine won’t crank, go on to Test
6.
TEST 6 - CHECK BATTERY
DISCUSSION:
Battery power is used to (a) crank the engine and (b)
to power the control board. Low or no battery voltage
can result in failure of the engine to crank, either
manually or during automatic operation.
PROCEDURE:
A.Inspect battery Cables:
1. Visually inspect battery cables and battery
posts.
2. If cable clamps or terminals are corroded, clean
away all corrosion.
4 2 3 5 6 7 8 13 11 9 10 12 14 15 16 18 17
178
1
7
8
183
178
183
239
178
178
178
239
183
15C
15
15A
15C
15E
183
START
239
178
15C
15
15C
15E
178
TS2
SW2
PCB
3
1
2
6
4
5
SW1
183
15
15
15A
239
178
178