How many diodes in an alternator (external regulator)
 

Well, any educated guesses. I am looking infos on a 74 2.7CIS alternator with external regulator.

Ingo

I would say that for a 3 phase alternator, you need two diodes to rectify each phase for a total of 6.

Then you need 3 more for the diode trio.

My opinion is 9.

Haynes shows 9 diodes...

Well, 9 is what I thought until a guy at the alternator shop claimed 8. I am lost here.

He was also talking about "isolation diodes" - what the heck is that?

The answer is ... it depends on the mfr and chosen design! Excitation diode array isn't needed if the regulator is designed to use the B+ supply instead! Most American-designed alternators only have the six power rectifiers -- cheaper to build and fewer parts to fail!