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Nerding Alternators

>No. Mine really is an AL27X. I actually ordered the AL31X once and
>it turns out that is a mechanical mirror image of the 27. Dunno why
>Bosch shows it for the car. It looks like it would have to mount on
>the driver's side, as in no A/C compressor. Anyway, I did order
>the AL179X and it does have a different mount. They must have
>upgraded some time after changing over from the 5k to the 200.
>It must have been something like "OK boys. Now we're bringing
>out a new model and we're going to fix all the crap we've been
>selling for the last 6  years like the alternator and, oh yeah, let's
>fuse the cooling fan."

>Thanks for your interest and I sure wish I had known to ask you
>for the 100A setup goodies. Much cheaper. If any other 5K owners
>have been frustrated by a marginal charging system, they should
>give you a call.

DeWitt and Peter:
The differences between the AL27X and the Al 179X is the upper mounting (you
need the nose engine mount and 2 bolts to make this swap, the bottom
configuration is the same.  Audi went to a two bolt mounting system in the
179X for ease of swap more than anything else.  2 10mm bolts hold the 179x
whereas a single long 8mm bolt with nut holds the 27 (tough to get the 8mm
bolt started while holding the alternator, a mechanics bitch, btdt).  A 17mm
socket can get you both the top bolts on the 179 with relative ease in
comparison (front bolt in first, rear goes in fine blind).  BTW, the 179X is a
115amp unit as listed in the Bosch catalog.  I have found that some
readjustment of the lower mounting bracket (to the A/C compressor) is
necessary when doing this swap.  The lack of readjustment can also create a
really buggered gear adjusting nut (BTseenT).  Regarding the AL31X, my
experience on this one is similar to the 109X installs (and a 109x -75amp
upgrade to 90amp).  I've only seen it on the 5000CD turbo/quattro, and the
bracketry is different on the bottom, but the top is the same as the AL27.  So
to update the 31x or 109x to the later style 27 you would need all the
brackets from the alternator and A/C mountings (+ the upper nose mount to do
the 179X).  Not really sure what the logic is on the 31 and 109, my guess is
that some of the cars that got them (the one I'm familiar with is an 88 5ktq
cd) were from some old stock mounting hardware audi had lying around (a
familiar problem).  The 109 - 75amp in the 88 car was barely enough charging
power, btw

My .02 on the swaps all together.  A 90 to 115 amp alternator swap will give
you a 20% increase in charging power.  Since all these upgrades require a
core, and the mountings, you will need to spend some time to get this
effective B4B.   Before considering it at all, make sure the splice in the
charge wire is healthy, the battery terminals are clean and secure, and the
connection at the starter is clean as well.  Several folks have done a new
charge wire to the battery with mucho success as well, btdt.  A good charging
90amp system should be fine for most tq's.  Is the 115 'better'?  Yup, but is
it the problem?

Scott Justusson