Bernina 180 thread breaking and tension problems

First make sure that you are using a new needle in the proper size. A needle with burrs on it will cause the bird's nest problem. Also, is the thread you are using old? My repair guy told me to keep my filled bobbins in the freezer to maintain their humidity, and that has made a world of difference in my stitching. Finally, how long has it been since you had the machine cleaned and serviced, and was it by an authorized Bernina repair shop? Bernina machines have special screws that only Bernina authorized repair people have - I discovered that when I took my machine in to someone who was not authorized only to have the timing go off in a matter of weeks. The authorized repair guy found clumps of thread that had been air blasted into the inner works of the machine and those clumps were getting caught up in the new stitching and causing the same problems you described. Good luck!

My problem is that I want to use yellow thread in the bobbin and either black or colorless on top in a baby quilt. I am trying to do a blanket stitch and the bobbin thread keeps coming on top or the black goes through to the botton. How do I set the tension so the yellow won't come through on top? or the colored threads wont' come through on the bottom? the bottom of the quilt will be yellow and the top is a combination of blue, red, yellow and white.