Ok this problem has baffled everybody i have brought it up against. maybe yall know something i can try... So my voltometer in my car reads about 14 when i start it up, perfectly normal. Then about 2 or 3 min later, it will literally JUMP to about 17.5 or 18. I just bought a new alternator thinking that was the problem, and no thats not it. so its not a regulator issue. Somebody mentioned something about a "goo" in the positive cable, then they squeezed it out and problem solved. But i do not have this "goo". I know its not a HUGE problem, but a problem that must be solved for the better of my electrical. Any ideas???? Ive checked everything! My battery is a little on the dead side, ive got 3 cells near shot, so i need a new one soon, but the problem isnt enough to cause a problem like this. One thing i noticed today, upon startup, my engine runs higher RPM's to warm up like everycar, but even when its warm, it stays around 1500... and i notice my voltometer is around 17.5 or 18, then, just outta the blue, the RPM's go down to about 750, and the volts go to around 14... what gives? BTW, this is an 89 RS with a 350.

 

If you suspect your battery is bad and needs replacing do it. Then if the problem continues now that you have a good battery check the volts with a multimeter at the battery and watch it there.

 

but would a slightly bad battery do all that?

 

batterys break down in different ways. i have heard of them actually switching polarity. i would change the battery before seeking other options. Sick

 

gotcha, thanks.