Hey there. 1984 300D recently developed a new trick. I turn on the car, it warms up enough for the blower to come on, it blows like normal for a few minutes, then something happens - the air sounds restricted and quits coming out of the vents at regular rate but rather seeps out of all vents. turn off the car and restart it and its back to normal for a couple of minutes.

any ideas?

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1984 300D "Brown (and Blue) Betty" Over 200k but the odometer isn't counting