Charging Issue?, I'm terrible at solving electrical problems Options

[sdoolin]

Voltmeter shows between 10V - 12V at idle (and everywhere else). Voltmeter drops to 10V when headlights, flashers, and wipers switched on. Multimeter across the battery terminals at idle reads 12.5V.

Alternator was verified good several years back when I built this engine.

I'm not sure what to check next?

[sdoolin]

OK, so I checked some more things, and I am NOT GOOD with a multimeter. But, here's what I found (all measurements at idle):

Battery = 12.5V
Green Wire from alternator and chassis ground = 4.5V
Brown wire from alternator and chassis ground = 0.05V (essentially 0)
Red wire from alternator and chassis ground = 13.8V

[fixer34]

OK, so I checked some more things, and I am NOT GOOD with a multimeter. But, here's what I found (all measurements at idle):

Battery = 12.5V
Green Wire from alternator and chassis ground = 4.5V
Brown wire from alternator and chassis ground = 0.05V (essentially 0)
Red wire from alternator and chassis ground = 13.8V

Assume red wire to chassis ground reading is being made at the battery positive terminal while the engine is running? Do the same measurement across the actual battery terminals. Voltage reading should be the same, or very close.

If it isn't, check/clean the battery terminal connections, the red wire connection to the positive post, the ground strap from battery to chassis, and the chassis strap underneath to the transmission. Unbolt and make sure the connections are clean/shiny.