hey guys.. picked up a 98 Silverado 1500 with the 5.7l... anyways when I drove it home after purchasing it the voltage gauge was bouncing around erratically between 12 or 13 to 15 or so volts. also the gauge cluster... headlights and tailights would pulse to this as well.. long story short it had a bad battery.. r/r the batt... much better... although I still would have a slight bouncing in the volt gauge and slight pulsing in the dash lights and headlights. I went to push on the post on the back of the alternator and it stopped the pulsing while I kept pressure on this post...

some sort of internal fault in the alternator? it's an old Delphi alt in there currently. I forget what that post attaches to inside the guts of the alt.

also the volt gauge bounces with the turn signals.. anybody found a solid fix for this... it seems that ppl just live with it being such a common problem

 

From what you say, it sounds like you need to repair or replace the alternator.

 

My 96 had the same problem. Replaced the alt. fixed the problem.

 

That's my take

 

Had the same issue for years. It became the normal for years. This weekend I upgraded my gauge cluster to the Cadillac Escalade cluster because it shows 120mph. No more voltage issues. It’s all the gauge motors in the cluster. They’re filled with oil and get dried out over time. Replace your instrument cluster panel with another one. Easy fix and way cheaper than an alternator. Junk yard $20-30