A lot has been written lately about the demerits of "off the cuff" information. I wrote what I thought at one time was an informative reply to a person on list and was rewarded with a smug "...this is completely wrong..." . I knew that I was right in what I said but incomplete on the subject which was the purpose of the isolation diode in the Motorola alternator so I chose to remain silent until I rehapened upon some literature to back up my claim. My statement was this ( as copied and pasted ) ;
You can run one of these Motorola alternators without the isolation diode but it is like replacing a fuse with a slug. The diode mounted in a red stamped steel heat sink plate on the back side of the alternator is there to protect the internal diodes which are much harder to replace. Clip your jumper cables on backwards and the isolation diode may go, but the circuit to the internal diodes should then be open and protected. Gary Walker A lister retorted ( apparently off the cuff ) so I dropped the subject, not having time to find a source to back me up. HOWEVER, now after almost a year, I happened to notice that on page 62 of Chilton's Copyright 1971 AMX & Javelin Repair and Tune Up Guide the following ; "The alternator generates three phase alternating current, which is changed to direct current by six silicon diodes. The entire DC output of the alternator is then passed through the ISOLATION DIODE. The ISOLATION DIODE, mounted on an external heat sink on Motorola models and internally on American Motors made and Prestolite alternators, is quite important, in that it, like all diodes, will pass current in one direction only. IT THEREFORE PROTECTS THE ATERNATOR FROM EXCESS BATTERY VOLTAGE FEEDBACK." ( I rest my humble case )