I did not read all of the Posts so this could be a repeat of info.

On my 84 300D the #12 fuse powers the Power Window Relay. When that fuse goes none of the windows work. Note that Fuse is shared with other items. That means on mine there is 3 fuses that can cause power window issues.

I suppose the Power Window Relay itself could also go bad but I have never read of anyone replacing it.

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84 300D, 82 Volvo 244Gl Diesel