Guardian Technologies 4270 manual Engine Protective Devices, Overspeed Protection

Section 5

ENGINE DC CONTROL SYSTEM

SHEATH	ASBESTOS	BODY	NUT
HEAT-WIRE
MAGNESIUM		INSULATING
OXIDE
POWDER		BUSHING
			CENTER
			ELECTRODE
Figure 5-11. – Glow Plug

ENGINE PROTECTIVE DEVICES

The engine will shut down automatically in the event of anyone or more of the following occurrences:

•Low oil

•High engine coolant temperature

•Engine overspeed

LOW OIL PRESSURE SWITCH

HIGH COOLANT TEMPERATURE SWITCH

The high coolant temperature switch has normally open contacts. This switch is immersed in engine coolant. If the coolant temperature should exceed 245-266 degrees F, the switches contacts will close to ground, sending a signal to the printed circuit board to shut down the unit via wire 85.

Figure 5-13. – High Coolant Temperature Switch

OVERSPEED PROTECTION

The oil pressure switch has normally-closed contacts. When the engine is cranking or running, oil will pass through the switch, which opens the contacts. If oil pressure should drop below 10 PSI, the contacts will close to ground sending a signal to the printed circuit board to shut unit down on wire 85.

ADAPTER

LOW OIL

PRESSURE

SWITCH

Generator A/C frequency signals are delivered to Terminals 5 and 6 of the engine control circuit board via wires 22 and 44. Should engine/generator speed exceed 69 to 71 Hertz for longer than 4 seconds, the circuit board will cause an engine shutdown.

Figure 5-12. – Low Oil Pressure Switch

Page 28