You have to close the bobbin-case door or you will get error codes.
Additionally, the bobbin sensor is calibrated for polyester sewing thread. Thin threads like Bottomline with give continual errors. I turned mine off.

What is the Yahoo site for the Bernina forum?? I too have problems with my sensor ---- took it in to the shop 3 times and it cleared for a few days ---then came back to visit. I finally turned the sensor off.

My 730 is also overly sensitive. I turned off the sensor for the bobbin area and all is fine. The top thread sensor seems to be adjusted perfectly. When the message boards were still up on the Bernina site, this question came up regularly and it appears to be a common issue with these machines.

thanks ill try that. karen in bakersfield

There is a yahoo forum on Berninas 630,640 and 730. I believe it also covers 430,440 and 435. I have found excellent advice there and it has covered this question extensively.

i turned the sensor off. just have to remember to use a full bobbin and remember to brush off the lint. hopes this helps anyone else. karen in bakersfield

i checked that ,it was going the way. if i leave the message up it sews fine . the message is annoying though. thanks, karen in bakersfield

I am not real familiar with Bernina yet but I did notice that you have to put the bobbin in the case with the thread unwinding to the right. Does this make sense. Maybe, you have it going to the left.

well i tried the cleaning, but iit didnt help. if i just leave the message on it sews fine, im wondering if i should turn that function off. karen

yes i have the gold bobbin. i have rethreaded and cleaned it . i also cleaned the eye on the bobbin door. i was in another room and someone suggested using a qtip with a tiny bit of alcohol on the hook and race, then reoil. i did this so i will try to embroider again and see if that fixes the problem. thanks so much. karen in bakerfield.

When I first started using my Artista 640 I would get those messages. You might try rethreading the machine including the bobbin. Do you have an embroidery bobbin too?

I have a bernina 730e and was wondering if anyone had a problem with the message check thread and clean bobbin coming up . i start to sew and after a few stitches the machine stops and the message appears. Thanks for any help. karen in bakersfield