88 Sliverado electrical flicker

In the morning my headlights flicker and the charge indicator needle bobs up and down for 30 to 90 seconds as if the alternator has gone bad. After the said time everthing seems to go back to normal.

The alternator is around six months old and shows no problems on a bench test. The battery test good, too.

I've cleaned the battery cables and tracked cables and wires to where the appear to be securely connected.

Did you check the battery? A severely undercharged, or bad battery can cause voltage fluctuations of several volts.

A bench test dont always tell if the alternator is good or bad . when you first start your truck the alternator is working its hardist to recharge the battery and maby failing under extream load. maby you need to get the high output alternator to make up for it...