Charge (battery) light randon upon startup - why?

[603Racing]

84' eta

Every now and then I get the charge (battery) light at startup. I also notice that the lights are dimm at the same time if they are turned on. I can also hear the fuel pump running at a lower pace. As soon as I blip the throttle the charge light turns off, lights get bright and the fuel pump runs at normal pace (normal pump hum). This random charge light happens randomly, I cannot replicate it. Day time, night time, hot, cold, rain, dry, on Mondays... you get the point.

What I've done - Main, fuel pump, and O2 relays have been replaced in the last month. New fuel pumps. Brand new voltage regulator. Alternator belt is correctly tensioned.

Battery is of an unkown age, Interstate brand. Engine cranks fine with no signs of a weak battery.

Any ideas?

[ddavidv]

Sort of normal. Revving the engine helps 'excite' the alternator into charging. Prior to that, you're just running on battery power. I've had this phenomenon with a few cars of the 70s-80s that have Bosch charging systems. My race car does this every time I start it.

[jlevie]

That could well be worn brushes (which can be replaced) in the alternator.

[FLG]

Sort of normal. Revving the engine helps 'excite' the alternator into charging. Prior to that, you're just running on battery power. I've had this phenomenon with a few cars of the 70s-80s that have Bosch charging systems. My race car does this every time I start it.

Same here, race car does the exact same thing (also have abs light and what not on until i blip the throttle) but charges fine always at 13.8

[603Racing]

I guess I'll live with it then and monitor for any changes in behavior. It only does it about once out of every 10 or so startups.

[603Racing]

Follow up on this thread. The issue got worse with the cold weather. Classic sign of battery problems. I replaced the battery 3 days ago, all is well so far.