Power Charging System Problems 91 gmc sonoma

[John d26]

I have a 91 gmc Sonoma with 4.3 v6 truck is bone stock,nothing aftermarket. Past month battery light flickers on and off volts fluctuate up and down on dash... Had battery,starter and alternator tested... Alt tested bad so bought and installed re manufactured one, still had same problem..so I was stumped and set up appt with local auto electrical specialist and he tested wire,connections, alt connects,starter,battery and all checked out but he said bad alternator and to buy new not remanufactured so I did from Napa auto parts $140 yesterday installed and doing same thing.. Truck will start up but will not continue 2 charge system.. I can drive it but not far worried if I'll lose total power or not and it will die.. At idle if i press gas peddle light will also go on and off... ??????? 91 gmc Sonoma 4.3 please help if any info thanks

[Duelin]

i would take it back to the electrical specialist and find out what he missed.