It is one far back in the fuse box.You need to remove wiper relay,fuse box lid,then unscrew two bolts holding the upper cower,and remove it.Then you will see bunch of relays in there.It should be the one in the midlle in the last row.I am not 100% sure,for the position but it is one of them,I had that same problem month ago

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Mercedes W140, S350TD, 95.
Mercedes W140, S350, 92.
Porsche 944, 86 N/A.
Porsche 944, 85 N/A automatic.
Porsche 944, 84 N/A.
Porsche 944, 83 N/A.
Opel GT, 73.
Toyota Supra MA61,84.