problem solved - dirt in the lock prevented the contact to activate the top raising.

 

The universal opening on the XK8 works from the door lock. You turn the key once and the doors unlock turn it again and "hold" the widows will go down and the top will open. If yours is opening the top after turning the key and releasing then most likely a micro switch in the door latch is sticking. Get a good can of spray lube and spray the lock opening and then open the door and spray the latch mechanism. As a last result you may have to remove the door card and clean and lube the latch assembly.