Automatic Bobbin Winder Problems: Fixing Overwinding, Not Starting, and More
Automatic Bobbin Winder Problems
The automatic bobbin winder should wind the bobbin evenly and stop when full. I see four common problems with these winders.
How the Automatic Winder Works
The winder uses a small drive wheel pressed against the main motor belt or handwheel. When you push the bobbin pin over, the drive wheel engages and the bobbin spins.
Detection Type
How It Stops
Pros
Cons
Mechanical arm
Arm moves as tension increases
Simple, reliable
Wears over time
Optical sensor
Light beam detects full bobbin
Precise stop
Lens can get dirty
Problem 1: Bobbin Overwinds
The winder does not stop when the bobbin is full. Thread wraps past capacity.
Cause
Fix
Mechanical arm spring weak
Replace spring or tension assembly
Optical sensor lens dirty
Clean with alcohol and cotton swab
Sensor wire broken
Solder or replace wire
Control board not detecting signal
Check voltage at sensor connector
The mechanical arm system has a tension arm that presses against the thread. As the bobbin fills, the thread pulls the arm outward. At a certain point, the arm triggers a switch that disengages the drive wheel. If the spring is weak, the arm never triggers.
Problem 2: Bobbin Winder Does Not Start
Cause
Fix
Bobbin pin not pushed over fully
Push pin firmly to the left
Drive wheel not contacting belt
Check rubber wheel for wear
Clutch disengaged
Push the bobbin pin harder
Motor not running
Check power to machine
Winder solenoid failed (computerized)
Replace solenoid
On computerized machines, the winder has a separate solenoid that engages the drive wheel. If you hear a click but the wheel does not move, the solenoid plunger may be stuck.
Problem 3: Noisy or Uneven Winding
Noise Type
Likely Cause
Fix
Grinding
Drive wheel worn flat
Replace rubber wheel
Clicking
Bobbin not seated correctly
Use correct bobbin type
Rattling
Loose winder assembly
Tighten mounting screws
Squeaking
Dry bearing
One drop of oil on pivot
Problem 4: Winder Engages While Sewing
This is dangerous. If the bobbin winder engages mid-seam, the thread feeds onto the empty bobbin instead of through the needle.
❌Engaged Winder While Sewing
The winder drive wheel can catch your fabric. Stop the machine immediately. The bobbin pin clutch is stuck in the engaged position. Spray a drop of Tri-Flow on the clutch mechanism and work the pin back and forth.
Our Sewing Machine Automation Guide covers all automatic features in one place.