Electrical Maintenance
80
Start Relay
The start relay (RL5) is mounted on the inside of
the control box. It is energized by the controller
after proper preheat time has occurred. When this
relay energizes, the starter solenoid receives
power and the engine cranks. If the start relay fails
in the open position, the engine would not crank.
If the relay failed in the closed position, the starter
would continue to crank after the unit started. The
RL5 LED on the PC board will light up when the
fuel pull relay is energized.
Preheat Relay
The preheat relay (PHR) is mounted on the inside
of the control box. It supplies power to the air
heater. If the preheat relay fails in the open
position, the air heater would not preheat and the
engine may not start, resulting in the cranking
time limit being exceeded. If the preheat relay
fails in the closed position, the air heater will
remain energized. The RL6 LED on the PC board
will light up when the fuel pull relay is energized.
Unit Wiring
Inspect the unit wiring and wire harnesses during
scheduled maintenance inspections for loose,
chaffed or broken wires. This will protect against
unit malfunctions due to open or short circuits.
12 Vdc Charging System
Battery charging current is supplied by a
transformer and rectifier utilizing current from the
ac alternator. The battery charging circuit
provides current to the battery until the proper
charge level is attained (13.1 to 14.6 volts).
The alternator exciter field is energized by the
SG+ controller. This initiates battery charging
approximately 15 seconds after engine start-up.
NOTE: The engine must run for approximately
15 seconds before the battery charging circuit is
energized. When the Delayed Cold Start feature
is set to ON, the controller shows “dELAY / AC”
screen and the alternator output remains off
until the engine temperature increases to 32 C
(90 F).
NOTE: The alternator exciter field coil (F1/F2)
for the SG+ and the µPG are different. The SG+
resistance reading is 13.9 ohms and the µPG is
2.3 ohms. In the photo below the µPG is on the
left and SG+ is on the right. The µPG will have
the external lead shown on the top of the coils.
See Service Bulletin C087 for more information.
1.
Start Relay (RL5)
2.
Preheat Relay (RL6)
Figure 40: Relay Locations
1
2
1.
External Lead on Top of µPG Coil
Figure 41: Alternator Exciter Field Coils
1
Summary of Contents for SGCO 3000
Page 4: ......
Page 12: ...SGCO 3000 Genset Addendum 12...
Page 14: ...Genset Model Features 14...
Page 22: ...Service Guide 22...
Page 32: ...Unit Description Features Options 32...
Page 78: ...Operating Instructions 78...
Page 86: ...Electrical Maintenance 86...
Page 114: ...Engine Maintenance 114...
Page 124: ...Alternator Operation and Diagnosis 124...
Page 130: ...Structural Accessory Maintenance 130...
Page 138: ...Index 138...
Page 140: ...Electrical and SG Menu Flow Diagrams 140...
Page 141: ...141 SGCO 3000 Wiring Diagram Page 1 of 1...