<E21> 1982 320i Loud Rattle Problem

[Peter Biernacki <pbiernac@xxxxxxxxxxxxxx>]

The car in question is a 1982 E21 320i 5-speed with the M10 engine.
Production date 12/81.

At above 3,500 rpm or so my car produces an extremely loud rattling
noise that seems to be coming from the area behind where the A/C
console is located.  I really don't know what is making the noise but
it seems to be only evident when the A/C is on.  Any clues or suggestions
on what it is and how to fix it would be greatly appreciated.
Thanks.

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