[Vwdiesel] Alternator

[Val Christian]

Milt,

The life of the bearings is almost limitless when the load and RPMs on
the alt are low.  On some of my cars I've kept the belt just a little
loose.  That's resulted in replacing a V belt every 4 or 5 years (100Kmiles
or better).  There's a little more wear on the pulley.  But this won't work
if you're running the defogger and the AC all the time.  

I did find that the 90A altenator I'm running on the 91NA is carried by 
Autozone.  In 1996, I needed brushes.  I eventually found some, but I
also found that AZ had the altenator for about $175.  In 1998, in the dead
of winter, I needed brushes again.  In a moment of weakness I went for the
AZ altenator, which had a lifetime warranty.  Since then, I've gone through
three "altenators" always just swapping out the brushes.  This next time,
I may just swap out the altenator - just in case.

The altenators have come with a load test sheet, showing the current output
vs. RPMs.  120A was not unheard of, and most put out 110A on the factory 
test.

Brushes seem to wear as some function of current draw.  I haven't figured 
out why and how, because the brushes are presumably just to activate a 
field. That field may change a little with higher output, but I haven't 
thought through the relationship that might exist.

One final thing, when we setup rally cars, years ago, we used to put smaller
pulleys on the altenators to get high output at low RPMS and idle.
We also cranked up the regulators (installed 20 turn trim pots externally).
This all worked just great.  Except it is not practical for a daily driver.
The altenators last about 10kmiles when they spin between 5 and 15 thousand
RPM all night long, and with large lighting draws on them.  For the guys 
into lighting, we used bars with four 4522 (or was it 4544) 250W 12V
aircraft landing lights, and four or six 4509 100W 12V landing lights.
At 14.3V they didn't last real long (the 4509s are rated 25 hours), but
they sure made a whiter light.  Q4509s, later with a different bulb
number, were made with quartz-halogen inserts on the sealed beam package
and lasted about twice as long and again were brighter.  HID would be so 
much nicer.  4509 bulbs are good for poor men though, because they are
only about $8 each, even today.  They put out a nice bow-tie pattern
from the filament.  Back to the altenators...we just kept a spare 
altenator on hand, and swapped out the bearings at our leasure.  I still
have a handful of altenators from my old A1s which have had one or more
bearing changes.  It would be a little harder with a serpentine belt,
because length matching is more difficult, and the smaller pulleys 
may be hard to find.

Oh, on the heat, when heating the screws, you don't want to get the case much 
above 150F.  This means working carefully, and quickly, and with a very small
tip.  If you're not going to open the case right now, I'd keep putting a 
drop of a light bodied penetrant on the screws periodically (once a week),
until you do break the case.  You may find that things come apart more 
easily at that time.

Best of luck.


Val

ps: If you live in Ohio, or parts of NY, you can pull the light bar, and 
point the lights at the engine for a preheat.  Grin.


> Hi Val,
>  
> Thanks for info.
>  
> I checked with Romaine Electric, here in Seattle. With my particiular Bosch alternator they have these parts; regulator, cup, diodes,sliprings. They said no screws or bearing but can probably "scrounge" some up if I come down.
>  
> They said to be careful using heat, which is understandable to get the screws loose. I will go ahead and install as is for now. Hopefully diodes and bearing are good.
>  
> Milton.