Hobart 120CU20, Operation And Maintenance Manual With Illustrated Parts List

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OM-2228 / Operation and Maintenance Manual
120CU20 / Series 500120 / 400 Hz. Generator Set
October 15, 2013 Chapter 1-1
Page 13
(1) Panel lights and panel light push-button switch (S74)
Meters are lighted from inside the control panel. The “ LAMPS ” push-button switch controls the
lights.
(2) Engine hour meter (M4)
The hour meter is electrically driven from the 12-volt DC battery system. The hour meter
measures and records the engine’s running time and will record up to 9999.9 hours on five
revolving drums. It is only functional when the engine is running.
(3) Engine oil pressure gauge (M24)
The oil pressure gauge is an electrical type that is connected by a wire to an oil pressure sensor
installed in the engine lubricating system. The range is 0 to 125 PSI (0 to 862 kPA).
(4) Engine ON indicating light (DS58)
When the engine is running at idle speed, a green indicating light, within the “ ENGINE START”
push- button switch, flashes at a rate of 1 second on, 1 second off. When the engine is running
at rated speed, the light will stay on continuously.
(5) Engine coolant temperature gauge
The temperature gauge is an electrical type that is connected by a wire to a water temperature
sensor installed in the engine cooling system. The gauge indicates engine coolant temperature in
the range of 100-280 º F (38-138º C).
(6) “ ENGINE START” push-button switch (S24)
The “ ENGINE START” push-button switch, when pressed, connects 12 VDC power to the starter
solenoid coil, which actuates the solenoid switch to connect power to the engine starting motor.
The 12 VDC power is supplied directly to the engine ECM and the oil pressure shutdown switch is
bypassed (This bypass is necessary for engine starting because the low oil pressure switch is
CLOSED until the engine is running normally). The green indicator light with blink.
When pressed a second time, this push-button switch provides a signal to the ECM to adjust the
engine speed to 2000 RPM. The green indicator light will glow continuously. At the same time, a
ground signal is provided to the regulator, enabling the generator to build up voltage for 400-Hz
generator output. Pressing the push-button switch once more removes these signals and the
engine reverts to idle speed and a blinking green indicator light.
(7) “ENGINE HEATER” push-button switch (S79)
The “ENGINE HEATER” push-button switch activates the standard cold starting aid (manifold air
intake heater), which is totally controlled by the engine’s ECM. Once the heater is activated, the
engine’s ECM will control the operation. The heater typically stays on for a period of
approximately 30 seconds, which is indicated by the light on the push-button. When the light
goes out, the engine is ready to start. Starting a cold engine without first warming the engine will
lead to excessive white smoke exhaust and the engine may be hard to start.