There are TWO fuses, I think you checked #19, but have you checked #6?
Also there's a combination relay (rect black box in fuse box) which completes the circuit from fuse #6 to provide (15 minute timer) power to rear defrost.

If you have service manual (look for the electrical diagram) & If you have a DMM...you can check for power & continuity of the rear defrost right at the relay.

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85' 190E w/collector plates