The circuit breaker is a switch that opens the battery circuit if the current in the electrical system goes higher than the rating of the circuit breaker.
A heat-activated metal disc with a contact point completes the electric circuit through the circuit breaker. If the current in the electrical system gets too high, the metal disc gets hot. This heat causes a distortion of the metal disc. The disc opens the contact in order to break the circuit.
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Find and correct the problem that causes the circuit breaker to open. This will help prevent damage to the circuit components from too much current. |
The speed sensor monitors the engine rpm by sensing the movement of the flywheel ring gear's teeth.
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| Illustration 1 | g00608052 |
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speed sensor | |
The speed sensor has wire that is coiled around a permanent magnet in order to generate a magnetic field. Voltage is produced as the teeth of the flywheel ring gear pass through the magnetic field. Positive voltage is generated when each gear tooth passes the magnet. Negative voltage is generated when the spaces between the teeth pass the magnet.
Water Temperature Contactor Switch
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| Illustration 2 | g00580098 |
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Water temperature contactor switch | |
The element of the water temperature contactor switch is installed in the water temperature regulator housing. The switch is nonadjustable. Thermal expansion of the element operates a microswitch. The switch can be wired to an alarm system or a shutdown in order to help provide protection from high water temperature. The element must be in contact with the coolant. The contactor will automatically reset when the coolant temperature is reduced below the threshold.
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| Illustration 3 | g00808031 |
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Air temperature contactor | |
The air temperature contactor is installed in the inlet air manifold. The switch is nonadjustable. Thermal expansion of the element operates a microswitch. The switch can be wired to an alarm system or a shutdown. The element must be in contact with the inlet air. The contactor will automatically reset when the air temperature is reduced below the threshold.
Water Temperature Sender and Engine Oil Pressure Sender
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| Illustration 4 | g00772013 |
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(1) Water temperature sender
(2) Engine oil pressure sender | |
The electrical resistance of water temperature sender (1) and engine oil pressure sender (2) changes in response to changes in the temperature or pressure. The senders are in series circuits with gauges. When the temperature or pressure is high, the resistance is high. When the resistance is high, the gauge will have a high reading.
In order for the water temperature sender to function properly, the bulb of the sender must be in contact with the coolant. If the coolant level is too low, the sender cannot detect changes in the coolant temperature correctly.
The senders require 24 VDC. The senders are used with protective systems that are energized to run.
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| Illustration 5 | g00776499 |
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Overspeed contactor | |
The overspeed contactor is installed on the magneto drive housing. The contactor is used in the self-powered protective system in order to help protect the engine from damage due to overspeeding. The contactor has a microswitch that is activated by high engine speeds. If the engine overspeeds, the contacts of the switch close. This grounds the ignition system in order to shut down the engine. If the switch is activated, the reset button on the contactor must be reset before the engine can be restarted. The speed for shutting down the engine can be adjusted on the contactor.
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| Illustration 6 | g00776696 |
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Engine oil pressure switches in the rear of the junction box | |
The engine oil pressure switch uses a spring loaded piston to activate a microswitch for a specific pressure rating. The switch is activated by low engine oil pressure. The switch can be used to activate an alarm or a shutdown.
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| Illustration 7 | g00580167 |
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Electronic speed switch (1) "VERIFY" button (2) "RESET" button (3) "OVERSPEED" LED (4) "OVERSPEED" adjusting screw (5) "CRANK TERMINATE" adjusting screw | |
The electronic speed switch has several functions.
Overspeed - The normal setting is 118 percent of the rated speed for the engine. Illumination of LED (3) indicates that the engine rpm has exceeded the setting. The setting can be adjusted with adjusting screw (4). If the engine rpm reaches the setting, the gas shutoff valve (if equipped) is de-energized and the magneto is grounded.
Reset - If an overspeed occurs, the reset button must be pushed before the engine can be restarted.
Verify - The "VERIFY" button is used to test the operation of the switch. When the engine is operated at 75 percent of rated speed, pressing of the button will shut down the engine. LED (3) will illuminate.
Crank Termination - This is an adjustable engine speed setting which signals the starting motor that the engine is firing and the cranking must be terminated. When the speed setting is reached, a switch will open in order to stop the current flow to the starting motor circuit. The starting motor's pinion gear disengages from the engine flywheel ring gear.