edge-we both have the same car- even the same color!
my acc acts up as well sometimes. try playing with the buttons and with the temp control dial- it should have a lock out click stop at either full heat (max) and full cold (min) - my off setting works
however..
there is another post about 'beating on the blower motor' you might try that as well if the easy stuff fails. good luck - bob

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1984 300D Turbo - 231k....totalled 11/30/07 RIP