Well a month or two ago my alternator went out and I had poor voltage to the battery in my 1991 RWD Auto Pickup. So I did the proper installation with a new alternator. A week or two ago my trucks alternator light just starts randomly flickering and now it seems to flicker about everyday. So I get home and check the voltage at the battery witch is 14.3 and all the fuses in the box and each fuse with the truck running is between 14-14.3 V. No clue on why it would flicker because the voltage is good all around and the light is starting to really get under my skin. If somebody had this issue it would be great to get some feedback with my problem, Thanks.

 

If the plug isn't in good-n-tight it's can do this. Same if the pins in the plug are dirty/corroded. A dab of silicon dielectric grease might be the cure. Make sure it's pushed in until the catch clicks. If the catch on the plug is broken, it will never lock in tight, too.

If the belt is slipping, it can cause this too. Make sure the belt is correctly tensioned up, and that the idler pulley is free to rotate. The idler bearings don't last forever.
Also, if you put a new belt on, it needs to be re-tensioned after only 5 minutes of run time, according to the FSM. Ever if it's been driven a ways, same thing. Recheck the belt's tension, if it was new.

Those are the two things I've found. Don't forget the alt's ground point, too. Check the large wire going over to the fuse block and battery is tight, and CLEAN at both ends.
Hope something in my rambling helps!
Pat☺