Help finding power seat diode/relay in 1991 190E 2.6

[brookspw]

Guys, this originally went out last year. SteveBFL and Gilly both attempted to help but my knowledge of electrical things left them short handed.

Here is that thread: Click here

Update:
-- Stereo works fine in all ways. It no longer comes on in an irregular patternwithout the key on (now, this might be because originally the bad diode allowed the current backflow, but now burned completely an allows nothing either way).
-- Seats do NOT work, at ANY time, with the doors closed. They will work at ALL times with the doors open.
-- Other than that, all electrical in my car works fine except my left door speaker only works about 1 day per month.

* I need to locate the diode/relay or whatever. If I have an electrical box UNDER my fuse box then I see NO way to get to it. There are NO screws, and even if there were, there would be no room to get to them and/or lift the top box out once loose.

Thanks for any help.