Friday, September 17, 2010

Journey of discovery: Ponderings

The instruments and the alternator field winding connection all are under the same screw terminal, powered from the ignition switch.  And the instruments come on when the ignition is turned on.

The oil pressure switch is not in the field circuit.  Do I need protection for the case when the ignition switch is on, but the engine is not running?  It seems like a good idea, but it adds additional elements into the charging circuit, and additional elements are additional potential failure points.  And the oil pressure alarm goes off when the ignition is on but the engine is stopped.  The only way to stop the alarm is to turn off the ignition.  The sound is obnoxious enough that the switch will not be left on.

  • Conclusion:  the oil pressure switch is unnecessary.  
  • Secondary conclusion:  the resistor is not needed, because the ignition switch will not be left on when the engine is stopped.
  • The problem is not likely to be the ignition switch
Other findings:
  • The other end of the cut-off brown wire at the starter solenoid is the red mystery wire in the cockpit engine control panel.  Now that I have identified it at both ends and can certify it as having no function, I pull the wire and discard it.  A little more confusion is eliminated.  I believe that the last of the mystery wires on the boat is now eliminated.
  • I identify for certain the wire which goes to the fuel shut-off solenoid.

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