what rpm does an alternator run at
This is a function of the ratio between the crankshaft pulley and the alternator pulley. Certain modified engines can have engine idles ranging between 600 to 1,500 rpm and red lines of over 8,000 rpm. These rpm, along with the pulley ratio, directly affect an alternatorâs performance and life expectancy. An alternator has a normal range of operation. Most alternators need to spin at about 2,400 rpm at idle, have their maximum output above 6,000 rpm, and should never exceed 18,000 rpm. So, how do you know how fast your alternator is spinning? The first step is to understand how the pulley ratio affects the alternator.