Overspinning alternator??

90FoxBdy

Founding Member
Jun 17, 2000
553
0
17
Linthicum, MD
While driving my car yesterday I noticed that on the highway while travelling about 3500rpms (c4 with 3.73) my battery light comes on and the volt gauge shows around 18volts. If I let off the light goes off rather quickly and volts bump down to between 14 to 16. I am pretty sure this just started. The combo only has around 200miles on it. I am running only the crank,wp, and alternator. Do I need a different(larger)alt pulley? Or is it a problem with the voltage regulator. Thxs
 
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What flavor of alternator? A 3G is good for about 15K RPM. If you know your crank pulley and alternator pulley dimensions, you can calculate the alternator RPM at 3500 engine-RPM.