need help asap

i recently took my ranger to get the alternator fixed, it was not charging. i had the alternator replaced, and now the voltmeter goes from 14-17 volts intermitantly, my battery light flickers occasionally, and my headlights flash. i took it back, and they said that a cylinder misfire was the cause of the voltmeter going back and forth, and that the battery and alternator are fine. is that possible, or could it be the voltage regulator in the alternator going out. thanks.

Sounds like a junk Alt to me.