Troubleshooting
118 Service Instructions 878-M PREMIUM - 03.0 - 10/2019
21.2 Errors in the sewing process
Error Possible causes Remedial action
Unthreading at seam
beginning
Needle thread tension is
too firm
Check needle thread tension
Thread breaking Needle thread and hook
thread have not been
threaded correctly
Check the threading path
Needle is bent or sharp-
edged
Replace the needle
Needle is not inserted
correctly into the needle
bar
Insert the needle correctly into the
needle bar
The thread used is
unsuitable
Use the recommended thread
Thread tensions are too
tight for the thread used
Check the thread tensions
Thread-guiding parts such
as the thread tube, thread
guide or thread take-up
disk are sharp-edged
Check the threading path
Throat plate, hook or
spread have been
damaged by the needle
Have parts reworked by qualified
specialists
Missing stitches Needle thread and hook
thread have not been
threaded correctly
Check the threading path
Needle is blunt or bent Replace the needle
Needle is not inserted
correctly into the needle
bar
Insert the needle correctly into the
needle bar
The needle strength used
is unsuitable
Use the recommended needle
strength
The reel stand is installed
incorrectly
Check the assembly of the reel
stand
Thread tensions are too
tight
Check the thread tensions
Throat plate, hook or
spread have been
damaged by the needle
Have parts reworked by qualified
specialists
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