Originally Posted by
BellaBoo
My Bernina did the same thing last week. I tried every tension setting I had and still got the thread difference. I called the Bernina shop and was told to use the same color in the bobbin and top. That worked. It only did this with the zig zag stitch.
Using the same thread in the top and bottom doesn't really solve the problem; it just hides it. However, if you don't want to spend the time trying to adjust the tensions, it is a quick fix.
With my Bernina, there is a hole in the "finger" of the bobbin case. When satin stitching, the instructions say to run the thread through the hole before inserting the bobbin case and bringing the thread up.
Be sure that before you start adjusting the tension, you mark where the original settings were so that you can return them after you have finished the project. A fine point Sharpie will work on the bobbin case to show where the screw was originally set.