Please review the previous post and the directions regarding the "voltage drop" test over the line. The circuit must be under load therefore the vehicle should be running with lights, blower, flashers all on.

Your meter is connected (Red) to Battery POSITIVE.
(Black) to the positive connection at the ALTERNATOR.

If you get a reading >.500mV you have a high resistance problem "somewhere" between the BATTERY and the ALTERNATOR, the next obvious connection in the circuit is the "Starter Motor" connection.