Mike wrote:

<snip>

> First, the old alternator has a small plastic box screwed to the back, with
> a black wire connecting it to a spade terminal on the alternator marked +.
> The plastic box is marked with a bunch of stuff, including a line reading
> "2.2uF 100V", indicating it's a smoothing capacitor of some sort. The new
> alternator does not have this piece. If it's just a smoothing cap, is this
> critical? i.e. would lacking this part cause the new alternator not to
> charge my battery? If it is critical, does this part have a name? I have
> not seen it referenced anywhere, in the Bentley manual or on the web.
> Should my new alternator have come with it?

I haven't looked at my '87 alternator lately, but I know the voltage
regulator is replaceable. It almost seems like your new alternator came
without a voltage regulator. Do you still have the old alternator?

> Second, the old alternator had the blue wire for the idiot light connected
> to a spade terminal labelled D. The new alternator has an empty hole marked
> D with no spade terminal, and a different hole marked W that _does_ have a
> spade terminal.

The blue wire goes to the idiot light, but its presence is absolutely
critical to the charging system. Alternators can not deliverer any power
unless the field winding is energized, and the field winding does not
get energized unless the alternator is delivering power. To overcome
this, if the alternator is not delivering enough power to energize the
field winding, the current that goes through the idiot light and the
blue wire is used to energize the field winding until the alternator
starts putting out current. So, disconnected blue wire = no power from
alternator. Again, it seems like your new alternator has a dummy plate
put in in place of the voltage regulator.

The W terminal is used for the tachometer on diesel engines. Since there
is no ignition system on diesels, is was common to take a signal from
the alternator, before the diodes, to run the tachometer. These days,
they probably use crank sensors like on a gas engine.