You can fix a black and decker cordless trimmer auto feed not working issue by clearing debris from the spool housing or replacing the line if it has tangled. Most of these feed problems happen because the line has welded together or the spool is simply empty.
Reasons your cordless trimmer feed fails
The auto-feed mechanism relies on centrifugal force to release more line as you trim. If the line is tangled or fused inside the spool, it can’t move freely to extend. Dirt, grass, and mud can also build up inside the spool cap, creating friction that prevents the mechanism from clicking forward. Additionally, if the line has been wound incorrectly—meaning it overlaps itself—the tension becomes too high for the motor to pull it out during operation. Always check the official Black and Decker support guide for your specific model to see if there are unique tension settings.
Clean the spool housing
To clear dirt from the cap, press the tabs on the side of the trimmer head to remove it. Pull the spool out and wipe away any dried grass or mud with a dry cloth. If the line is stuck, pull out a few inches and check for loops that look tight or knotted. If the line is damaged or too short, replace the entire spool with a factory-wound one. If you can’t remove the cap without using force, stop and check your user manual to avoid breaking the plastic tabs.
Check your line winding
If your spool isn’t empty, the line might be wound too tightly or in an overlapping pattern. Remove the spool and unwind the entire length of the string. Inspect the line for any flat spots or melted sections caused by friction. Rewind the line neatly, ensuring the string stays in its designated channel without crossing over itself. This is a common mistake that causes the line to bind mid-operation. If the line is brittle or old, it will keep breaking inside the head; replacing it with fresh, high-quality line usually solves the issue. This works best if you keep the line tension consistent while winding.
Replace the internal spring
The internal spring sits under the spool and pushes it against the cap to control the feeding action. Over time, this spring can lose its tension or become clogged with debris. If the spring is bent, missing, or stuck, the auto-feed won’t trigger regardless of how clean the spool is. You can buy a replacement spring kit for most models. This is for users who feel comfortable working with small, loose parts. If you aren’t sure how to reassemble the head, take a photo of the parts before you remove the spring so you can put them back in the correct order.
What not to do
- Don’t use metal wire or thick rope as a replacement for trimmer line, as it will damage the motor and void your warranty.
- Don’t force the trimmer head against hard surfaces like concrete to “bump” the feed, as this damages the plastic casing.
- Don’t attempt to modify the internal gear assembly with oil or grease, as this attracts dust and creates a thick sludge.
- Don’t continue running the motor if you smell burning plastic, as this indicates the line is permanently fused.
How to stop it happening again
Proper maintenance prevents the feed mechanism from jamming during your next yard session.
| If you’re doing this | Do this instead | Why |
|---|---|---|
| Cutting near fences | Stay two inches away | Avoids welding line to wire |
| Using old, dry line | Keep line in a damp place | Moisture keeps the line flexible |
| Ignoring line tangles | Rewind the spool properly | Prevents knots from forming |
| Forcing the trimmer | Let the motor reach speed | High speed triggers the feed |
Frequently asked questions
Can I use any type of string for my trimmer?
No, you must use the specific diameter line recommended in your manual. Using a line that’s too thick will strain the motor, while a line that’s too thin will break constantly and fail to feed through the eyelets properly.
Why is my trimmer line constantly breaking?
The line likely breaks because you’re hitting rocks or hard edges while trimming. If the line is old or has been sitting in the sun, it loses its flexibility and becomes brittle, which causes it to snap off inside the housing before it can feed.
How long should the trimmer line be when I start?
The line should extend to the edge of the guard on your trimmer. If the line is too short, the centrifugal force won’t be strong enough to pull the mechanism forward, and if it’s too long, the motor will struggle with the weight.
Is it safe to open the trimmer head?
Yes, it’s safe to open the head as long as the battery is removed first. Never perform any inspection or cleaning while the battery is attached, as the trimmer could start unexpectedly and cause injury to your fingers or hands.
What happens if I lose the spring inside the head?
If you lose the spring, the auto-feed will stop working entirely because there’s nothing to push the spool into the correct position. You’ll need to order a replacement spring specifically for your model number to restore the feeding function.
Final Thoughts
If the feed still doesn’t work after you’ve checked these parts, it’s time to inspect the spring inside the spool cap for any damage. Replacing a worn-out spring is an inexpensive fix that’ll get your tool running smoothly again. You won’t have to worry about your yard work being interrupted anymore.
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Dorothy Addeo is a senior product reviewer at Safefins.com with years of experience testing kitchen, furniture, backpacks, and everyday lifestyle products. She focuses on comfort, durability, usability, and long-term value through hands-on research and real-world testing. Her goal is to help readers find reliable products with honest, easy-to-understand recommendations they can trust.