You know how it is... You sew on your machine for days, months or years, and suddenly it doesn't work as it should.
(in my case mostly when the employees have used the machine... strange! :roll: )
Usually the problem is quickly found, such as an incorrectly inserted needle, or a piece of thread that has wound itself under the housing of the bobbin of the lower thread, etc. Recently my co-worker had another problem with our Pfaff 545:
The tension of the upper thread was always distorted by itself. Sometimes the tension was normal and at the next seam it was much too loose again... when I finally found the problem after hours I felt, I immediately thought: "Shit! This is a really unusual problem... you have to share this in the forum. "

The problem was a broken spring in a part I don't even know what it's called. So I try to describe where the problem was...
So when lifting the presser foot with the knee lever (or foot pedal), the plates that regulate the tension of the upper thread are pressed out of each other with a metal pin (photo of the front).

This metal pin is controlled by a metal sleeve on the back of the sewing machine. (photo of the back)
In this metal sleeve is a small spring that presses the metal sleeve downwards when the sewing foot is lowered. This causes the metal pin of the tension of the upper thread to slip back into the starting position.
If the spring is broken, there are fluctuations in the tension of the upper thread, because the metal sleeve positions itself more or less high depending on the gravity and oil level of the parts.




The removal of the necessary parts is quite simple and should be no problem for anyone who can build a seat apart. I replaced the spring in an emergency by a spring of a ballpoint pen..... This works great so far! :sweat: :lol:

I hope that this post will help some of you to save some time, nerves and money in the future. :wink: