Apparatus for identifying faulty diodes in automotive alternators

Abstract From the Canadian patent

Faulty alternator diodes are identified by detection of a voltage ripple across the terminals of the automotive storage battery. A diode is forward biased whenever the battery has adequate charge to be designated a "good battery", and the forward bias condition is utilized as a reference potential. A voltage divider scales the reference potential and couples, it to the inverting terminal of a comparator. The non-inverting terminal is biased at a predetermined differential from the inverting terminal and the, probe signal is AC coupled to the non-inverting terminal. If a diode is bad the superposition of the AC with the bias will switch the comparator and energize a light emitting diode.