[Cntrysthbst]

Is the plug on the back of the alt plugged in good?

Are the battery terminals clean and on good?

Is the positive coming from the alt tight?

Have you called the dealer to ask why? Seems your problem started after they did their work on it. If I could figure out why mine is doing something simular to this I could help you more, this is all I can think of for now. Good luck! And welcome!