Symptom check first, because it decides everything downstream. Trigger pulled, motor audibly spinning, blades sitting still: that's a drive problem. A trimmer that's completely dead, no motor sound at all, is a different fault (battery, safety switches, or the switch itself). This guide works the first case, then covers the dead-tool fork at the end.
Here's what the behavior tells you before you touch a tool:
| What you observe | Most likely cause |
|---|---|
| Motor spins, blades never move | Jam, or stripped gear/cam in the housing |
| Blades start, drag, squeal, then stop | Dried sap binding the bars |
| Blades stall the moment they bite a branch | Oversized branch or bent/dull teeth |
| No motor sound at all | Battery, two-hand safety, or switch failure |
Step 0: pull the battery
Before your fingers go anywhere near the bar, take the pack off the tool. Every check below except the very first one happens with the battery out and gloves on. A hedge trimmer that frees up mid-cleaning will cost you a fingertip.
1. Rule out the cheap stuff (two minutes)
Nearly every cordless hedge trimmer requires two switches pressed at once: the front loop-handle switch and the rear trigger. Release either and the blades brake to a stop, by design. Grip both fully and completely before deciding anything is broken.
Then the pack. Seat it until it clicks, check the charge gauge, and if you own another tool on the same battery platform, test the pack in that tool. A pack showing one bar can spin a motor unloaded and still fold the instant the blades take a load, which reads like a jam but isn't.
2. Clear the jam
Battery off. Most 22 in. homeowner bars are rated for branches in the 5/8 in. to 3/4 in. range. Feed one a 1 in. limb and the wood wedges between the teeth, locks the bar, and leaves the motor turning against a stalled blade. Pull wedged wood out with pliers, then brush chips and clippings out along the entire bar, both sides. Don't pry between the two blade bars with a screwdriver; that bends a tooth and trades one problem for a worse one.
3. Dissolve the sap
Resin from a season of cutting dries into a varnish that glues the two reciprocating bars together. The signature is specific: blades move when you first pull the trigger, then drag, squeal, and freeze. Spray the bar with a resin solvent or blade cleaner, work the blades back and forth by hand a few strokes, wipe the residue, then oil the full length with light machine oil. The whole job takes ten minutes. Make the spray-and-wipe a 30-second habit at cleanup and this failure mode mostly disappears.
4. Sight the bar
Hold the trimmer up and sight down the blade bar end to end. One bent tooth is enough to pinch the bars and stop the stroke. A minor bend can be dressed straight with pliers. A kinked or cracked bar means a replacement blade set, which most brands sell as a service part for less than half the tool's price.
5. The gearbox verdict
If the bar is clean, oiled, straight, and free of debris and the motor still spins with zero blade movement, the drive between motor and blades has failed. Inside the housing, a gear (often nylon) turns an eccentric cam that converts rotation into the back-and-forth stroke, and one hard jam can strip that gear in a single event. This is the repair-or-replace line. On a homeowner-grade tool, the gear, the cam, and the teardown time usually total more than the trimmer cost. Check the warranty first: tool warranties in this category typically run three to five years, though damage from forcing oversized stock through the blades may not be covered. On a pro-grade unit, a gearbox rebuild at a service center is worth pricing before you buy new.
Normal behavior vs. a dead tool
Blades that stop the instant you release either handle are normal; that's the safety brake doing its job. Slow, creeping movement in cold weather that wakes up after a minute points to thick old grease in the gearbox, worth a service but not urgent. If nothing moves while the motor runs after steps 1 through 4, that's mechanical failure, see step 5. And a tool that's fully dead with a known-good pack from the same platform has a failed switch or motor, which lands in the same repair-or-replace math as the gearbox.
The pattern across all of it: jams and sap account for most of these calls, and both are free fixes. Clean the bar, oil it, cut within the tool's branch rating, and the gearbox generally outlives the batteries.