1674916 Volvo.Penta Expansion tank

Electrical System
Two electrical systems are available to provide engine protection. In each case, engine shutoff is achieved by grounding the magneto. Each system is also capable of activating the gas shutoff valve if provided.1. For the self-powered protection system, oil pressure (OP) and water temperature (WT) protection are provided. When combined with a mechanical overspeed contactor switch (MOS) [(provided standard on engine)], full protection is obtained. An energized-to-shutoff (ETS) gas shutoff valve (GSOV) is available which is activated by magneto voltage.2. An energized-to-run (ETR) non-auto-start-stop protection system provides OP, WT and OS (overspeed) protection. An electronic speed switch (ESS) is used for the OS protection. This system is fully independent and requires an external 24 volt power source and an energized-to-run (ETR) gas shut-off valve.Electrical Schematics And Wiring Diagrams
Electrical schematic foldouts are provided in this section with the text for each protection system. Use the electrical schematics to follow the circuit operations of the protection systems.Point-to-point wiring diagrams for the protection systems, junction boxes, and starting, charging, and tachometer circuits are located in the Wiring Diagrams Section of this module. Use the diagrams for component position layout.Components
The components that follow may be used on one or more of the two protection systems available on the 3406 spark ignited engine.Electric Service Meter
The electric service meter group is self-powered. A magnetic pickup mounted on the flywheel housing provides voltage (starting at 200 engine rpm) to power the electric service meter which records clock hours with quartz accuracy. A separate magnetic pickup must be used for each service meter; it cannot be shared with the digital tachometer, electronic speed switch, or electronic governor magnetic pickup.Water Temperature Contactor Switch (WTS)
A water temperature contactor switch is located in the cooling system. The unit is nonadjustable. Thermal expansion of the element operates a micro-switch that signals the shutoff solenoid which causes engine shutdown. The water temperature element must be in contact with the coolant. If overheating occurs due to low coolant level or no coolant, the sending unit will not function.The water temperature sending unit can also be wired into an alarm system or light to signal high water temperature. After an overheated engine is allowed to cool, the contactor automatically resets itself.
Contactor Switch (Water Temperature)Magnetic Pickup (MPU)
Magnetic Pickup
(1) Clearance dimension. (2) Magnetic pickup. (3) Wires. (4) Locknut. (5) Gear tooth. (6) Housing.The magnetic pickup is a single pole, permanent magnet generator made of wire coils around a permanent magnet pole piece. As the teeth of the flywheel ring gear go through the magnetic lines of force around the pickup, an AC voltage is made. A positive voltage is made when each tooth goes by the pole piece. Each time the space between the teeth goes by the pole piece, a negative voltage is made. Engine speed is then determined by the frequency of these signals.Mechanical Overspeed Switch (MOS)
The overspeed contactor is used in a self powered protection system to protect the engine from damage due to overspeeding. It contains a micro switch that is activated by high engine speed. The overspeed switch is mounted on the tachometer drive. If the engine overspeeds, the switch contacts close and connect the magneto to ground to shut down the engine. When the engine shuts down because of overspeeding, the overspeed contactor switch must be reset by pushing reset button. The overspeed contactor switch is adjustable.Circuit Breaker (CB)
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 electric system gets too high, it causes the metal disc to get hot. This heat causes a distortion of the metal disc which opens the contacts and breaks the circuit. A circuit breaker that is open can be reset after it cools. Push the reset button to close the contacts and reset the circuit breaker.
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.
Circuit Breaker Schematic
(1) Reset button. (2) Disc in open position. (3) Contacts. (4) Disc. (5) Battery circuit terminals.Oil Pressure Switch (OPS)
Oil Pressure SwitchThe oil pressure switch uses a spring loaded piston to activate a micro switch for a specific pressure rating. This type of switch has better accuracy over the operating temperature range and uses a much higher electrical contact rating to improve reliability.Slave Relay (SR)
This is a standard type relay that, when energized, has contacts that open across one circuit and close across another circuit. The circuits are wired so that voltage from the magneto goes to the spark plugs when the relay is energized. When not energized, the relay causes magneto voltage to go to ground. This relay is not used on the self-powered protection system.Emergency Stop Switch (ES)
The emergency stop switch has two normally closed contacts. When pressed, magneto voltage is grounded and the gas shutoff valve (GSOV) is closed. The engine will be prevented from starting until the switch is manually reset.Electronic Speed Switch (ESS)
Electronic Speed Switch (ESS)
(1) Verify button. (2) Reset button. (3) "LED" overspeed light. (4) Seal screw plug (overspeed). (5) Seal screw plug (crank terminate).The Electronic Speed Switch (ESS) is designed with controls built into a single unit to monitor several functions at the same time. The functions that the ESS monitors are:Engine Overspeed (OS)
This is an adjustable engine speed setting (normally 118% of rated speed) that prevents the engine from running at a speed that could cause damage. This condition will cause a switch to close that shuts off the fuel to the engine and connects the magneto to ground to stop current flow to the spark plugs.Crank Termination (CT)
This is an adjustable engine speed setting that signals