Methods for detecting a short fault of an alternator rectifier electronic component include sampling a field winding voltage or current signal of an alternator, during operation of the alternator, and determining a fault ripple period at which the alternator field winding signal exceeds a fault threshold. A short fault of an electronic component of a rectifier coupled to the alternator is detected in the event that the fault ripple period closely matches an alternator armature period. Alternatively or additionally, the sampled field winding signal is band pass filtered, and a short fault is detected in the event that an amplitude of the band pass filtered field winding signal exceeds a fault threshold. The methods can be implemented, for example, by an apparatus that includes a hysteresis frequency counter, a frequency comparator, and a countdown timer.