Got home and it wasn't the usual F11 fault - this time an F15 - servo motor for the contra rotator fault.
I think the fault is reported if the servo motor doesn't activate one of the two travel monitoring switches at each end of the gear mechanism in time.
When I looked the right switch was almost activated but not quite.
Easy ish fix.
Remove back.
Remove the screw (T40 I think) in the middle of the drive wheel for the drum.
Pull off the drive wheel (watch for the washer in the middle).
Lubricate the 'S wave' mechanism with spray grease and test movement by pushing on the cog gear.
Reassemble by puting on the drive wheel - watch out for a free floating ring bearing inside the hole - use your finger to hold it centred while you put the wheel back on.
Re attatch with the torx screw.
Now the difficult bit - the belt is very tight. Not sure if there is a correct way of doing this but I put the belt over the motors and rotated the drive wheel while hooking the belt over the edge - a bit like putting on a bike chain. Watch out for the edge of the drive wheel as it is sharp (cut my finger).
Anyway - test up - should be working now.
Darren
August 2011