I found the answer in past replies. The 1a250v fuse is in the module behind the kick panel where the speaker is. Pull out the module, take it apart and there it is.
Onboard computer works now but I don't have any instructions as the owners manual I have is for an '85 instead of an '83. The onboard computer was upgraded.
Does anyone know where I can get instructions for the Bedienteil BC300T4E?