Wire Continuity; Check Field Boost - Guardian 4700 Repair Manual

Section 7
DIAGNOSTIC TESTS
VOLTAGE RESULTS
WIRE 2 & 6
EXCITATION WINDING
VOLTAGE RESULTS
WIRE 11 & 22
POWER WINDING
SENSE LEADS
ROTOR
AMP DRAW
(MATCH RESULTS WITH LETTER AND REFER TO FLOW CHART – Problem 2 on Pages 22 & 23)
3. Set the VOM to measure AC voltage.
4. Disconnect Wire #2 from the DPE breaker (CB3) and connect
one test lead to that wire. Disconnect Wire #6 from the Voltage
Regulator and connect the other test lead to that wire. Start the
generator and measure the AC voltage. It should be above 60
volts. Record the results and stop the generator.
5. Re-connect Wire #2 to the DPE Circuit Breaker (CB3) and re-
connect Wire #6 to the Voltage Regulator.
6. Disconnect Wire #11 from the Voltage Regulator (VR) and con-
nect one test lead to that wire. Disconnect Wire #22 from the
Voltage Regulator (VR) and connect the other test lead to that
wire. Start the generator and measure the AC voltage. It should
be above 60 volts. Record the results and stop the generator.
7. Re-connect Wire #11 and Wire #22 to the Voltage Regulator (VR).
8. Remove the jumper wire between Wire #4 and 12 volt supply.
9. Set the VOM to measure DC amps.
10. Connect one test lead to the 12 volt fused battery supply Wire
#15, and connect the other test lead to Wire #4 (should still be
disconnected from the VR).
11. Start the generator. Measure the DC current. Record the rotor
amp draw.
12. Stop the generator. Re-connect Wire #4 to the Voltage
Regulator.
TEST 5- WIRE CONTINUITY
DISCUSSION:
The Voltage Regulator receives unregulated alternat-
ing current from the Stator Excitation Winding via
Wires 2, 6 and 2A. It also receives voltage sensing
from the Stator AC Power Windings via Wires 11 and
22. The regulator rectifies the AC from the Excitation
Winding and, based on the sensing signals, regulates
Page 32
A B
ABOVE ABOVE
60 VAC 60 VAC
ABOVE BELOW
60 VAC 60 VAC
1.0 - .85 A 1.0 - .85 A
± 20% ± 20%
TEST 4 RESULTS
C D
BELOW ZERO OR
60 VAC RESIDUAL
VOLTAGE
(5-12 VAC)
ABOVE ZERO OR
60 VAC RESIDUAL
VOLTAGE
(5-12 VAC)
1.0 - .85 A ZERO
± 20% CURRENT
DRAW
that DC current flow to the Rotor. The rectified and
regulated current flow is delivered to the Rotor
Brushes via Wires 4 (+) and 0 (-). This test will verify
the integrity of Wires No. 0 and 2A.
PROCEDURE:
1. Set a VOM to its "Rx1" scale.
2. Remove Wire No. 0 from the Voltage Regulator, fourth terminal
from the top. The Voltage Regulator is labeled next to terminal(-).
3. Connect one test lead to Wire No. 0 and the other test lead to a
clean frame ground. The meter should read continuity.
4. Disconnect Wire No. 2A from the Voltage Regulator, sixth ter-
minal from the top. Disconnect the other end of this wire from
the Excitation Circuit Breaker (CB3). Connect one test lead to
one end of Wire No. 2A and the other test lead to the other end
of the same wire. The meter should read continuity.
RESULTS:
If continuity was NOT measured across each wire,
repair or replace the wires as needed.
If continuity WAS measured, proceed to Test 6.
TEST 6- CHECK FIELD BOOST
DISCUSSION:
Field boost current is delivered to the Rotor only while
the engine is being cranked. This current helps
ensure that adequate "pickup" voltage is available to
turn the Voltage Regulator on and build AC output
voltage.
Loss of the field boost function may or may not result
in a problem with AC output voltage. If the Rotor's
residual magnetism is sufficient to turn the Regulator
on, loss of the function may go unnoticed. However, if
the Rotor's residual magnetism is not enough to turn
the Regulator on, loss of field boost can result in fail-
ure of the unit to generate an output voltage.
E F
BELOW BELOW
60 VAC 60 VAC
BELOW BELOW
60 VAC 60 VAC
á1.2 A
1.0 - .85 A
± 20% CURRENT
G
ABOVE
60 VAC
ABOVE
60 VAC
ZERO
DRAW