The great advantage of battery-powered outdoor equipment (OPE) is reliability. With few moving parts, your chainsaw, blower, or trimmer runs with minimal maintenance. The core of this dependability is the brushless motor—a sealed, highly efficient powerhouse.
However, even brushless motors fail. Because they are often integrated directly into the tool, replacing the motor usually means replacing the entire tool head or power unit. Knowing the specific warning signs of a failing motor can save you hours of wasted time and allow you to leverage your tool’s warranty before a total breakdown.
The Brushless Advantage (And Why They Fail)
Unlike old brushed motors, brushless motors use electronic sensors and controllers to switch electromagnetic poles, eliminating physical wear components like carbon brushes.
Why They Last: No brushes means no friction and far less heat, leading to exceptional longevity.
Why They Fail: The two main failure points are not mechanical, but electrical and thermal:
- The Controller/Circuit Board: The electronic brain that manages power delivery.
- The Windings/Magnets: Damage caused by extreme heat or impact.
⚠️ Four Key Signs Your Brushless Motor is Failing
Listen and feel for these specific symptoms that indicate the motor, or its control board, is reaching the end of its life:
1. Intermittent or Pulsing Operation
The motor runs fine for a second, then cuts out, pulses, or suddenly loses torque, even with a fully charged battery.
- The Cause: This is often a sign of a failing speed controller or circuit board. The board might be misreading sensor data or experiencing thermal overload and cutting power erratically to protect itself.
- Action: If a simple battery swap doesn’t fix it, this points squarely to an internal electronic fault.
2. Excessive Heat and Odor
The motor housing itself (near the shaft) becomes excessively hot to the touch after only a short, light period of use, accompanied by a distinct smell of burnt plastic or burnt electronics.
- The Cause: Thermal overload. The motor windings may be starting to break down, or a bearing (one of the few mechanical parts) is failing, causing excessive friction. Increased resistance in the windings generates extreme, damaging heat.
- Action: Stop using the tool immediately. Continued use will lead to total failure.
3. Distinct, New Noise
Listen for anything metallic, scraping, or grinding—sounds that were not present when the tool was new.
- The Cause: While not strictly the “brushless” component, bearing failure is the most common mechanical breakdown. As the internal bearings wear down, the rotor can start to scrape the stator windings, leading to permanent motor damage.
- Action: Bearing replacement can sometimes be done by a repair shop, but due to integrated designs, often the cost approaches that of a new tool head.
4. Sudden, Significant Power Drop
Your high-power chainsaw suddenly struggles with limbs it previously sliced through easily, or your blower delivers noticeably less airspeed, even on the highest setting.
- The Cause: This can be a sign of a shorted winding. If some of the fine copper wires inside the motor short out, the motor loses part of its electromagnetic strength, leading to a permanent reduction in torque and power.
- Action: Check the battery first, then confirm the tool attachment (chain, trimmer line) is not mechanically binding. If the problem persists, the motor is compromised.
💸 The Replacement Reality
Unlike gas engines, which can be rebuilt or tuned, electric brushless motors are typically sealed units.
- Handheld Tools (Trimmers, Blowers): If the motor is the issue, it’s usually more economical to purchase a new power head or replace the entire tool. The labor cost to tear down and replace the internal motor often exceeds the cost of a new unit.
- Mowers/Large Equipment: Higher-end mowers may have easily replaceable motor modules, making repair more viable.
Always check your warranty first! Most manufacturers offer a warranty (often 3 to 5 years) that covers motor and electronic component failure. A failing motor is a clear warranty claim.