How to Fix E15 Thread Break Alert With an Intact Upper Thread

Introduction

If the screen shows a thread break alert, but the upper thread is still intact, the bobbin thread may be running low, out of thread, or feeding incorrectly. This is one of the most misleading alerts on an embroidery machine — the sensor is detecting a break, but the problem is not where you’d expect it to be.

Before you rethread the upper thread (which is still fine), check the bobbin side. In most cases, the fix takes less than two minutes and does not require any disassembly beyond opening the bobbin compartment.

Follow the steps below to troubleshoot the issue:

1. Check the Bobbin Thread Level
2. Check the Bobbin Winding
3. Reinstall the Bobbin
4. Run a Low-Speed Test

Step 1: Check the Bobbin Thread Level

First, pause the machine and open the bobbin compartment cover.

Remove the bobbin case and check how much bobbin thread is left.

If the bobbin is nearly empty, that alone explains the alert. The sensor detects the sudden loss of tension as the thread runs out, even though the upper thread never broke.

Step 2: Check the Bobbin Winding

If the bobbin is nearly empty, out of thread, loosely wound, or unevenly wound, replace it with a full and evenly wound bobbin.

Step 3: Reinstall the Bobbin

When reinstalling the bobbin, make sure it is installed in the correct direction.

Guide the thread through the bobbin case slot, and underneath the tension spring. Gently pull the bobbin thread to make sure it feeds smoothly with slight resistance.

Reinstall the bobbin case and make sure it is securely locked in place.

Step 4: Run a Low-Speed Test

Before continuing the project, lower the embroidery speed and run a short test. Check that the bobbin thread feeds normally and that the stitches look even on both the front and back of the fabric.

If the test stitches look clean, resume your project at normal speed. If the alert comes back, recheck the bobbin direction and tension spring seating — those are the two most common remaining causes.

Tutorial Video

If you prefer to follow along visually, the video below walks through the same four steps in order — from opening the bobbin compartment to running a low-speed test. You can watch it before you start or use it alongside the steps above.

Conclusion

A thread break alert with an intact upper thread is almost always a bobbin-side issue — not a broken thread. Check the bobbin thread level first, then the winding quality, then reinstall the bobbin in the correct direction with the thread properly seated under the tension spring. A low-speed test confirms the fix before you commit to the rest of your project.

If the alert keeps coming back after all four steps, and the bobbin looks correct, contact HTVRONT Support at support@htvront.com — there may be a sensor or tension issue that needs professional attention.

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