BMW Repair: Convertible Top is not working, 1992 bmw 325i, bmw 325i

Question
I have a 1992 bmw 325i convertible (car is dated as 05/92) body E30. I have a fully automatic convertible top. When I bought this car gear which moves arm for top itself is broken but motor works fine (I tested with 12 volt battery) motor disconnected though so i can fold top manually. Motor for booth is fine and gears is fine - disconneced as well so I can fold top and close booth and I use two wires from battery to tighten booth so it can lock top inside. But My convertible top button is not working it does not make motors spinning. I thought I could replace fuse or relay so it can work but I couldn't find fuses or relays for conv.top. I found only black box with wires coming from motors in trunk is this unit should be replaced? And what is BC mark on turn signal handle? Thank You.

Answer
Alexsey,
 Good work so far, your information is a great help.

 I would check the switch it's self to make sure the switch is working.  You can pop it out, and clean it with some contact cleaner (get this from local parts store).  These switches regularly go bad, so thats probably you issue.

 The BC mark on the turn signal is for a the on board computer.  If you look to the right of the radio, you will see the computer with "date, time, mileage, MPH, etc....  If you press the turn signal in it will activate this computer to do what ever desired function you selected.  Just push the end of the turn signal onto it's self and you should hear a click.  This switch works in conjunction with the on board computer (OBC).

  Hope this helps,
   Josh