I noticed every once in a while my alt. light flashes real quick at idle. The engine doesn't miss, aftermarket volt meter reads over 14 and doesn't flicker. It will just flash maybe once a minute or not at all. It is so quick I had to deliberately sit and watch it to see what the light said. '88 DLX 3.0 5spd

 

I know this sounds stupid and maybe my truck is demented but mine does it when the master cylinder is low.

Not kidding

 

alternator brushes? easy fix did mine a few years back.

 

Mine did that right before the alt died on me.

 

Thanks.

 

Could also be a ground issue. The wiring, harnesses & connections/connectors are all getting old & brittle. Check all the major grounds (ECU, fusebox underhood, frame, engine, body, etc.).

 

That maybe the case rabbit, I would imagine the volt meter would flicker when it flashes.

 

Update, my alternator stopped charging, I replaced the brushes just 5 dollar fix. Bearings and relator seemed in good shape.

 

Probably not (but you just determined that yourself!) An "automotive" voltmeter has lots of damping, if for no other reason than to keep the needle from jiggling on rough roads. I would be surprised if it reacted fast enough to catch anything you'd call a "flicker."