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Some recent history for this vehicle:

  • The battery had stopped charging.
  • Alternator bench test passed.
  • Battery bench test passed, but "in late stage of life".
  • Reinstalling the original alternator seemed to have eliminated charging issues.

Then, a few days later...

The car would not crank. Suspecting the starter, I took it out and bench tested it. It seems to be functional.

I checked some voltages. Keep in mind the battery has not charged in about 10 days and has been under some load (hazards ran for an hour during towing, bench testing the starter, various attempts to start the car).

Anyway, here are the voltages:

  • 12.3 @ battery (no load)
  • 12.3 @ + wire @ starter (no load)
  • 11.8 @ starter signal when key turned

What could the lower voltage @ the starter signal mean? What else should I check?

Thanks!

voltage drop tests pending

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    Welcome to Motor Vehicle Maintenance & Repair! – Pᴀᴜʟsᴛᴇʀ2 Dec 28 '18 at 1:14
  • What happens when you jump b+ to the starter s terminal? Have you charged or replaced the battery? Are there any other loads that come on when the key goes on like headlights or the blower? – Ben Dec 28 '18 at 3:34
  • If I understand correctly, the big lug on the starter has 12.3v, and the small wire on the starter gets 11.8v when the key is turned. This should be sufficient for the starter to start. If this is correct, I would be looking at a loose connection, or a bad starter. The solenoid could be failing. Try tapping the starter with the handle of a screwdriver, or lightly with a rubber hammer. This will sometimes be enough to make a connection and get it to work. If this works, replace the starter. Are the multiple studs on the back of the battery you might have mixed up? – rpmerf Dec 28 '18 at 13:02
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Measure voltage drop when key is cranked at battery Compare battery voltage at starter wire (not signal wire) when cranked Anything less than 9.5-10v is a dead battery Also comparing voltage at battery and starter lead post will tell you if voltage drop is caused by corroded/loose cable-also check earth connection to starter

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