TP-6519 8/1744 Section 4 Controller
Disabling the generator set. Accidental starting can
cause severe injury or death. Before working on the
generator set or equipment connected to the set, disable the
generator set as follows: (1) Move the generator set master
switch to the OFF position. (2) Disconnect the power to the
battery charger. (3) Remove the battery cables, negative (--)
lead first. Reconnect the negative (--) lead last when
reconnecting the battery. Follow these precautions to prevent
starting of the generator set by an automatic transfer switch,
remote start/stop switch, or engine start command from a
remote computer.
Relay Board Replacement Procedure
1. Access the controller junction box to locate the
relay board. See Figure 4-9.
2. Disconnect relay board harness connector P3
from connector P14 on the relay board.
3. Pull the faulty relay board off the four mounting
standoffs inside the junction box.
4. Press the new relay board onto the four standoffs.
5. Connect three-pin connector of harness GM52639
to P14 on relay board GM51403. See Figure 4-10
and Figure 4-12.
6. Verify that harness GM52639 is securely connected
to P11 on the control board. See Figure 4-11 and
Figure 4-12.
7. Verify that harness GM52639 is securely connected
to the engine harness. See Figure 4-12.
4.8 Silicon Controlled Rectifier
Module
The silicon controlled rectifier (SCR) module works with
the ADC-RES to regulate the output voltage. The
ADC-RES monitors generator output voltage and
adjusts the excitation current to the rotor through the
SCR module. The SCR module location is shown in
Figure 4-1.
The SCR module is powered through stator leads 55
and 66 connected to SCR terminals AC1 and AC2.
Leads G connected to terminals G1 and G2 provide the
controller signal. Leads FP and FN connected to the
positive (+) and negative (-- ) SCR terminals provide
excitation current to the rotor. See Figure 4-15 and the
wiring diagrams in Section 7.
The SCR module is protected by a 20-amp fuse (F1) on
the controller. Check the fuse and replace it, if blown.
In the case of output voltage problems, check the
controller configuration and settings. Then test the SCR
module using the following procedure.
GM28483
G1
G2AC2
AC1 --
+
Figure 4-15 Silicon Controlled Rectifier (SCR)
Module
SCR Module Test Procedure
Required equipment:
D Ohmmeter
D 12-volt test lamp (or voltmeter)
D 12-volt DC power source
D 100--500 ohm resistor
D Jumper
1. Set the ohmmeter to the R x 1 scale.
2. Connect the ohmmeter from (+) to (--) on the SCR
module. You should read high resistance in one
direction and low resistance in the other (reverse
the leads).
3. Connect the ohmmeter from AC1 to (+) on the SCR
module. You should read high resistance in both
directions.
4. Connect the ohmmeter from AC1 to (--) on the SCR
module. You should read high resistance in one
direction and low resistance in the other.
5. Repeat steps 3 and 4 for AC2.
6. Connect the ohmmeter from G1 to (+) on the SCR
module. You should read low resistance in both
directions.
7. Repeat step 6 for G2. You should read low
resistance in both directions.
8. See Figure 4-16. Connect the negative (--) lead
from the D C power source to the positive (+)
terminal on the SCR module.
Note: The SCR module may be damaged if the
power supply is connected incorrectly. Be
sure to connect the negative lead from the
battery to the positive terminal on the SCR
module.
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