[Vwdiesel] Alternator mix and match

MLightner mikel at buncombe.main.nc.us
Tue Jan 23 09:16:24 EST 2007

Greetings Volks folks,

Once again hoping for some of ya all's excellent guidance and/or 

Due to the overall semi-clapped out state of  my daily-driver 
project-car-85 Jetta (A/C, no PS), I wasn't too surprised to find that I 
needed to do something with the alternator if I was gonna be able to 
continue to drive it. It came with two clapped-out alternators, only one 
of which has a W terminal on it - it's bearings are rather noisy and 
free-spinning and the plastic bearing carrier on the back bearing no 
longer  has a snug fit in the housing.  The other alternator's bearings 
have a more normal feel to them but are also, though considerably 
quieter, still a bit noisy when mounted to the engine.  Also, on the 
second alternator, the rear bearing is a bit smaller, as is the wiring 
of the stator.

Judging from the different sized rear bearings and the stator's 
wire-size, my guess is that I have a 90 amp and a 65 amp alternator, the 
one with the W terminal came with the offset pulley so I guess it's 
probably the Jetta's original. 
(Is there such a thing as forensic auto mechanics? If so, I feel I'm 
being initiated into it by this car).  To buy some time, swapped the 90A 
stator-rectifier assembly into the 65 amp housing and, after a lot of 
spacer-shuffling at the pulley, ended up with a decently aligned and 
very much quieter alternator with a tach output.  I unplugged the wires 
to the A/C clutch, since I don't expect to be needing it.That brings me 
to my questions:

    1) how hard is it to remove the bearings from one of these 
armatures? I have a bearing puller I've used before on electric motors, 
but it seems there was more clearance behind the bearings on the ones 
I've previously used it on - just wondering if there's any special 
tricks that might come in handy during non-destructive disassembly.

    2) The two armatures look identical except for the smaller rear 
bearing, could it be that they are indeed the same?

    3) From reading in the archives and elsewhere I've gathered that to 
add a W terminal to an alternator you just need to solder a wire  to the 
Y junction of the three stator coils, can anyone confirm this?

Thanks in advance for any info.


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