Can An Alternator Regulator be bad then good?

[supra-raleigh]

On a 99 Aurora while driving and at idle, the message on the onboard computer indicated a low reading on the voltmeter, dropping to as low as 10volts or so. This issue persisted for the next few times I tried to drive the car over the couse of about a week. Now the car seems to be operating within normal voltage readings from around 12v to 14.9v. This begs the question:

Can an alternator regulator go from one moment not working properly and then working properly?

 

[C&C]

More likely, and I'm guessing here, maybe a loose ground wire. I would check battery terminals for clean and snugness and maybe even engine/chassis ground(s).

 

[supra-raleigh]

Voltage Drop Test

So, I should visually inspect the wires and run a voltage drop test across the negative battery terminal and the body of the alternator?

 

[supra-raleigh]

Three Years Later, And The Same Issue Has Come Up Again

The problem went away but has returned. The car is not charging the battery and voltage drops while car is running. This caused the car to stall.

The battery light on the dash comes on when the key cycles to the on position. The light turns off like normal when I start the car. I thought it should stay on if there is a no charge problem.

The car was jump started using the under the hood battery post and a ground on the engine bracket. I let the cables on to charge for about 15 minutes before starting the car, then started it and had enough battery power to get the car home 5 blocks away.
I then charged the battery to a full 12.6V with the battery in the car.

Any Ideas?