I am trying to understand the wiring to the console warning buzzer and how it might relate to a faint glow we are getting in the oil pressure warning light,(opwl).
Looking at the electrical schematic in the engine manual (drawing #200360 rev C), it shows that the warning buzzer gets positive 12v power from the I pole on the key switch. It is intended to buzz if either the engine overheats or the oil pressure drops. The engine overheat side seems simple. As I read it the heat switch is grounded.It is connected to the C terminal on the buzzer. If the engine overheats the switch closes and provides a ground to the buzzer so the buzzer goes off. The same function lights the overheat warning light which is also connected to the C terminal.
The oil pressure side is much more confusing. Positive battery power is connected to one side of the oil pressure switch. That is then interconnected to a pole on the alternator and then on to the buzzer (this is the route that gets positive power to the buzzer). If I read it correctly when the engine runs the oil pressure switch is closed and power flows across the switch and on to the fuel lift pump from there It also sends power on to the preheat solenoid and to the P terminal on the buzzer. But it appears that if the oil pressure fails the switch will open and it won't be sending power to the P terminal. In that circumstance the buzzer should go off. How does it do that with no ground?
Here are my symptoms:1.There is a faint glow in the opwl when the motor is running. I get that even if I pull both wires off the oil pressure switch.
2. The buzzer does not come on when I turn the key on before starting the engine.
3. The fuel lift pump does not come on when I turn the key to preheat.
4. The opwl comes on brightly when I turn the key to preheat.
5. The buzzer which appears to be original says 24v on the back. It used to sometimes come on when the key is turned on but now never does. It also sometimes makes a very quiet buzz that comes and goes.
The boat is hull#123. We recently changed the oil pressure switch which was not supplying power to the fuel pump. The new one has the fuel pump working fine. We are planning to replace the preheat solenoid and the buzzer, but I still can't see how the buzzer will work if it does not get grounded. Any thoughts?
Sorry for the long post.
Bob
Lazy Dog #123
Console buzzer wiring
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