Journey of discovery: Operational testing and direct measurements

I ate lunch, drank a beer, and thought about this some more.

And then I decided to take another approach.  Clearly my assumption that the problem was a bad wire (or perhaps the oil pressure switch - my first assumption) was incorrect.

So, I got out my voltmeter and checked the voltage directly at the terminal 1 connector.  (I probably should have done this much earlier.)  When the ignition switch was on and the engine stopped, I saw 13.1 volts - battery voltage (and I had to ignore the low oil pressure alarm, screaming in my ear).  This is as it should be.

Then I started the engine and kept it below 1000 RPM.  I still was seeing the 13.1 V at terminal 1.  Then I wiggled the connector around a bit and the voltage shot up to 14.1 - the alternator had started running, and was feeding itself.

I was able to repeat this several times.

Treating the connector with WD40 and plugging/unplugging it several times did not help.

Conclusions:

• The problem may be a bad connection internal to the connector, where the wires join the terminal.
• The problem may be a bad connector, making a poor connection with the alternator terminals (actually, these two terminals are on the internal voltage regulator).
• The problem may be a loose connection at the voltage regulator, inside the alternator
• The problem may be a bad voltage regulator.
• The exercise was worth it, in understanding how the wiring actually is run, and in removing the last mystery wire from the boat.  I will make a note on the schematic reflecting the actual wiring.

At a minimum, I need to get a new connector.  And I may have to pull the alternator and disassemble it to check the internal connections (I made every one of them, years ago when I installed the non-stock voltage regulator in it).

But I'm tired.  Having gotten this far, I'll leave the next stage for another day.

I hear a beer calling to me (faintly, from inside the refrigerator)...

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Journey of discovery: Operational testing and direct measurements