The battery on my 1991 190E 2.6 keeps draining with fuse 12 in the car. When I pull fuse 12, the battery doesnt drain and I can start the car without jump starting it. What component on fuse 12 can cause this?

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1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)