They are essentially the same for use on a waterboxer. The only
important difference is the AL33X is supposed to have an extra lead for
diesel vehicles and the AL27X may not but obviously waterboxers are all
gas. The extra diesel lead is the "W" lead. It is sometimes present on
the AL27X but is supposed to be always on the AL33X. Another small
possible difference is the connection for the small blue wire but it is
trivial to adapt if it doesn't match.

The early waterboxer alternator used a spade connector for the small
blue wire while the later waterboxer alternator used a ring connector.
The rebuilt replacements can come both ways and usually have the extra
part to adapt your blue wire end to the other style if needed.

Mark

Jeffrey Vickers wrote:
> Got a friend with an 87 2WD Westy and he needs an alternator. Looked
> online and it looks like there are two choices of Bosch remanufactured
> units - AL27X and AL33X - how do I know which one he needs? (I don't
> have access to the van for a few days so I can't have a look at it )
>
> Thanks,
> Jeff
>
>