Random alternator not charging issue.

[Tim's Buick]

When I go to start it, very randomly, the light is on and my guage shows not charging. I can shut the car off and restart a time or two, and it will start charging.

Alternator is new. Had the same problem before. I had to replace the alternator because with that many miles, the bearings were starting to grind pretty loud.

What controls the charging on these? My brother had a similar problem on an olds with the 3300 that turned out to be a wire for the guage chafing on a metal grounded part.

BTW, another thing, the alternator seems a wee bit slow to turn on most of the time on startups. Always been that way. Start the car up and no guage activity. Then a second or two later, the alternator turns on and everything brightens up.

Thanks guys

[J Wikoff]

That's something I've wondered myself.

[dpalyu]

I have a 95 Bonneville with the same problem. Changed ECM (PCM) and that fixed problem. Charge was intermittent. Changed 2 batteries and 3 alt. replaced battery cables and cleaned all body grounds. Did not fix problem. Computer fixed problem.

[Bob Dillon]

What controls the charging on these? My brother had a similar problem on an olds with the 3300 that turned out to be a wire for the guage chafing on a metal grounded part.

All alternators in the modern era have internal voltage regulators, and they're really just a chip. The chip in yours is bad. Swapthe alternator again, make sure all your wires are intact, and the problem will almost certainly go away.

BTW, another thing, the alternator seems a wee bit slow to turn on most of the time on startups. Always been that way. Start the car up and no guage activity. Then a second or two later, the alternator turns on and everything brightens up.

Thanks guys

Have you checked your belt tensioner or serpentine belt? Sounds like slippage to me.

As to the PCM, to my knowledge, nothing in the PCM regulates alternator output.