PLZ help battery at 18 volts after 4000rpm??

well the only way i noticed this is at night. all of a sudden at 4000rpm my headlights and dash lights would go super bright on me. so i hooked up a mulitmeter and reved past 4000rpm and there it was 18+ volts at the battery.

just wanted opinions im leaning towards volt regulator. dammm this alternator is only like 6 months old …and its on its 4th alternator. it has warranty so i guess ill get new one.

also i have been having bad problem with the car sputtering like 3 cyls. im wondering if that might be the source of this problem too. the sputtering isnt after 4000rpm it is itermitent.

It’s the alternator. You’ll probably notice that it will kick out less than 12v at idle (probably 6-8). Replace your alternator (unless the broken alternator part can be replaced cheaper). If this is allowed to continue, it will eventually fry your battery.

And your wiring…