Here are a few sites that may be helpful in diagnosing your problem:
NUMBER ONE SUGGESTION--install a brand new needle. Sewists are known to be very frugal about changing needles but it is usually the easiest and least expensive fix for a lot of problems.
Remove all the thread from your machine, clean the bobbin area of any lint, threads, etc. Be sure that you RAISE the presser foot BEFORE you thread the upper thread. This releases the tension disks so the thread will seat properly. Now, re-thread from the beginning verifying you are following the correct threading sequence (consult your manual).
The standard factory tension setting is the midpoint, ie of the range is 1-10, set the tension at 5 and then adjust from there.
Why is my thread breakingWhy Does My Top Thread Keep Breaking Sewing MachineWhy Does My Thread Keep Breaking While SewSewing Machine Problem 1 Thread Breakage
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The standard factory tension setting is the midpoint--midway between the highest and lowest. Tension will need to be adjusted to suit the needle, thread, and fabric for the current project. A sewist should be comfortable making these adjustments to achieve the best tension. The correct tension is achieved when the upper thread and bobbin thread meet in the middle of the fabric--neither the bobbin thread is pulled to the top of the fabric nor is the upper thread being pulled to the underside of the fabric.
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I know this question was posted a long time ago, but just in case anyone else has the same problem thought I'd share this: it's from the instruction manual for the Elna 2003, 2005, 2007.
try rethreading the machine top & bobbinput in a new needlemake sure the bobbin is not over woundmake sure the bobbin is turned the right way in the bobbin casemake sure the bobbin case is inserted correctly in to the machineif the machine still doesn't pick up the bobbin thread it's possible thatthe machine is out of time
SKIPPED STITCHES
1.the needle is not inserted correctly
2.the needle is damaged
3.the wrong size needle is being used
4.the foot is not attached correctly
Check that your needle is fully up into the needle housing, and is in flat shank to the back.Also change the needle if it has been in the machine for more than 6 hours of sewing as the needle will go blunt and this can make squeaking or popping sounds as you stitch.Lastly, are you sure that the bobbin case is in correctly and hasn't been put in incorrectly. It should have a stitch finger which locks up into the top of the rotary hook if its a vertical bobbin case and bobbin design which I'm pretty sure your machine is.