Alternators (from almost a year ago) off the cuff scruff- you may not want to read- but all of Gary's stuff is informative or at least funny! I hope.

["Gary Walker" <NashFlash@xxxxxxxxxx>]

  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 )

    The text goes on to list two other benefits of the isolation diode and 
a " SIDE BENEFIT" as quoted in the text, that is, according to my detractor, 
the sole purpose of the item in question.   (  Which  in my humble opinion 
only comes into play, by the way, if one or more of the internal diodes have 
already become partly or completely shorted internally and are thus leaking, 
which goes back to the isolation diode which is probably already shot at 
this point.)   ( I have had meters since the seventies and know how to use 
them and I also have an alternator spin up testing machine. )    I have a 
lot to learn but I did not fall out of my tree yesterday, Mr. Crooks.
              Your AMC Friend,
               Gary Walker,   owner of some old AMC stuff,  including the 
Grant Rebel F/C  et al
P.S.   I'll have another stroke at the bloke that believes that any time a 
change is made to a part in process of production that the part number ( 
casting, stamping or whatever ) always changes.    They MAY, but I assure 
you they do not always change.   I just completed 30 years of hellacious 
work with GM.   I know Jack AND Jill.