Had the same problem with my '88 Westfalia. The condenser coils are "wrapped"
in the black foam you describe. If you look closely at the Bently manual you
will see this loosely diagramed in the section on removing the cabinents in
the Westfalia.  I waited for a year and was still dealing with foam blowing
out - so I took the ac housing out and cleaned out all the foam. Decided to
make the most of it and installed larger rear stereo speakers while I had the
overhead cabinents out.

You might be able to vaccuum out most of the foam by removing the rearmost
overhead panel in the rear of the van where the A/C air is sucked in from.
Anyway you approach this - it is not a 'fun' task.

Ssittservl wrote:

> The air conditioner vents on my '87 Westflia have suddenly started
> spewing black foam - small chunks of some sort of semi-deteriorated
> open-cell black rubbery stuff.  It looks like the remains of a filter of
> some sort.
>
> I've looked in the vents and the air inlet with a flashlight, and I don't
> see any filter.  Similarly, my Bently manual doesn't show anything.
> Anyone know what it is, and if there's any way to get to it short of
> disasembling the whole A/C enclosure?  Or is it not really needed
> anyway, and I should just wait for it to all blow away?