CYLINDER GP-HYDRAULIC 3967144 - Caterpillar

High Water Temperature Shutoff
The shutoff switch is located in the water temperature regulator housing. Excessive water temperature closes the switch. No resetting procedure is required: As the coolant cools, the switch opens.
The sensing element must be submerged in the coolant to operate. A low coolant level cannot actuate the shutoff.
Low Oil Pressure Shutoff Switch
This device is usually mounted on the side of the engine with oil lines connected to the switch. Low oil pressure closes the switch.Manually operated systems require resetting by pushing the button on the switch until it latches. After the engine is started and oil pressure builds, the knob will return to the extended position.
This switch cannot provide protection if the reset knob does not move to the extended position after the engine starts.
Automatic start-stop systems use a switch which resets itself.Overspeed Shutoff Switch (Electro-Mechanical)
This switch is mounted either on the tachometer drive or on the governor. Excessive engine speed closes a switch by centrifugal force. To reset the switch, push the button marked RESET. The knob will remain down until the engine overspeeds. Overspeed Shutoff Switch (Electronic)
This switch uses a flywheel housing mounted magnetic pickup to sense engine speed. The control box is mounted on the engine block. Excessive engine speed closes a circuit breaker. To reset switch, push arm of breaker to the run position. Fuel/Oil Pressure Switch
This switch is mounted in the fuel manifold between the clean side of the fuel filter and the fuel injection pump housing. Low fuel pressure (below 3 PSI, 2 kg/cm2) opens the switch after the engine has been stopped by one of the above shutoff controls. This switch prevents the battery from discharging after the engine is stopped. The switch can be used to de-energize the shutoff solenoid after stopping the engine, or to open the circuit between the alternator regulator and the charging alternator after the engine is stopped.This switch is also used on automatic start-stop applications equipped with an electric governor. In this application, when adequate oil pressure is reached, the switch closes to allow the electric governor to control engine speed. This switch does not require resetting.Mechanical Shutoff Control
The mechanical shutoff control consists of a low oil pressure and an engine overspeed shutoff device. On 6 cylinder engines, the mechanical shutoff is mounted on the side of the engine. On V-engines, the shutoff is mounted in the vee between the two banks of cylinders. A high water temperature shutoff may be installed in the temperature regulator housing. If either an overspeed condition, or a low oil pressure condition occurs, a spring-loaded rod is tripped inside the control which moves and holds the rack in the shutoff position. If a high water temperature condition occurs, the excessive heat causes a valve to move in the temperature sensor, which dumps oil flowing to the low oil pressure shutoff. The low oil pressure actuates the low oil pressure shutoff to stop the engine.Long periods of cranking can trip the low oil pressure shutoff and prevent the