Any Lamella sun roof boffins out there?

[mun802]

A bit of a long shot and I'm not expecting many (if any) replies but, here goes anyway. Roof is closed -some may say leave it that way- but when I select open nothing happens. Unshipped both motors and they motor over when closed selected but nothing when selected to open. switch has been removed and checked and appears okay. is there a relay for open only?
incidentally its a ML270.

Thanks.