I have a problem with my s10 2.2l -97 pickup. The radio flashes off and on and the volt meter drops down a little bit and headlights seems to dim. It all happens very fast so maybe something more happens to. I have tried to search if any cables behind the radio is loose but i cant get it to fail. I have looked in the motor space but nothing seems to be wrong. but as soon as I drive the car it starts to flash. What can I look for? Im sorry about the writing im not so good in english, hope someone understand my problem anyway.......

 

Check the grounds to the body as well as both battery cables.
sounds like your alternator may be the culprit though

 

Had the same problem recently on my Blazer, eventually while driving home, dials and lights on dash went crazy, next time I pulled up the revs dropped and engine stopped. Battery totaly flat. Had to replace the alternator and everything is ok now. First sign was slow turnover on the starter first thing in the morning.
Adrian