I had the fan out of it's housing and sitting on the pass. floorboard to witness the abrupt stop, start and speed changes, so not a vacuum issue with vents. I'll check those blower regulator posts. Thanks. Any other ideas?

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1984 Astral Grey 300TDT - The French Fry
1979 Yellow 300SD - The Pomme - SOLD
1985 Light Ivory 300DT - Fritz
1987 Anthracite Grey 300SDL - ?