Electircal "freak out"... Altenator?

I just purchased a used 2001 Yukon XL from a wholesaler. When the vehicle was delivered, he stated that it had been sitting awhile in the wharehouse and he had to jump to start. I noticed at that time that the battery light shown in the "message center" at start up.. and then goes off. A couple of days later, the battery was too weak to start. I trickle-charged the battery that night and it ran fine for a few more days. However, the battery light continued to come on at start up. A few days later the battery was too weak to start again. Without much thought, I replaced the battery. It has been a couple of days now and my wife just called to say that the truck is "freaking out" electrically. By that she meant that the dash lights and interior lights and compass on the rearview mirror were randomly going on and off, although it was still running fine. She turned it off and upon restart all was fine. Any ideas? Altenator?

I would say the voltage regulator is getting ready to take a s#$t in the alternator.

Hi,
is the alternator belt tight?
What does the Voltmeter in the instrument panel say when you go from idle to revving it?
Some car parts places will check the charging system.
Take care, Eggert :bananasmi