Why is my drill losing power or smelling of burning?
Working out whether the problem is the battery, the supply, the bit, the vents or the motor — in the order that costs least to check.
- Difficulty
- beginner
- Time
- 15 min
- Read
- 4 min
- Safety
- warning
Short answer
Check the cheap things first: a blunt bit, the wrong gear, a tired battery, or a long coiled extension lead. Then check the vents, which are the usual cause of overheating. A hot-varnish smell with heavy sparking from a brushed motor means worn brushes or a failing armature, and that is where repair economics start to matter.
Loss of power feels like a motor problem and usually is not. A drill delivers less to the work when anything in the chain between the supply and the cutting edge is degraded, and most of that chain is easier and cheaper to check than the motor. Working through it in order avoids replacing a tool that needed a new bit.
Safety
Step by step
- Rule out the bit first.It is free, it is the most common cause, and a blunt bit makes any tool feel underpowered. Fit a new one and repeat the same cut.
- Swap the battery or the supply.A known good pack, or a different socket and a shorter lead. This separates a tool problem from a power problem in about a minute.
- Look at the vents.Both sets, in and out. Compacted dust is the most common cause of a tool that has become hot and weak, and clearing it often restores it completely.
- Listen and smell carefully.Hot varnish and mild sparking on a brushed motor is normal wear territory. Hot plastic, smoke, or a change in the motor's note is a stop-now signal.
- Decide on the economics.Brushes and a chuck are cheap. An armature, a gearbox or an electronic controller usually costs more than a comparable replacement tool, and that is where a repair stops being sensible.
Tips
- A cable reel used coiled can only carry a fraction of its rated current before it overheats. Unwind it fully for any power tool, every time.
- Letting a labouring tool run at no load for thirty seconds pulls cooling air through it and does more good than putting it down hot.
- If a tool has always been marginal for the job rather than recently worse, it is not failing — it is the wrong tool, and hiring the right one solves it.
If it doesn't work
Drill feels weak but sounds normal
Cause: Blunt bit or wrong gear — Fix: Change the bit and drop to gear 1. Most complaints about a drill being underpowered are a blunt bit being asked to cut, and it is free to rule out.
Cordless tool runs strongly then fades quickly
Cause: Ageing pack losing capacity — Fix: Try a known good pack. If the tool is transformed, the pack has reached the end of its life rather than the tool.
Cordless tool cuts out abruptly and restarts after a pause
Cause: Protection circuit tripping on current or temperature — Fix: Use a larger pack, let it cool, and reduce the load — a smaller pack under heavy demand hits its current limit.
Corded tool weak on an extension lead
Cause: Voltage drop, often from a long or coiled lead — Fix: Unwind cable reels fully — a coiled reel under load also overheats — use the shortest adequate lead of a suitable rating, and plug into a socket rather than daisy-chaining.
Tool gets very hot and smells of hot varnish
Cause: Blocked vents, or sustained overloading — Fix: Blow the vents clear and let the tool cool completely. Work in shorter bursts, and use a bigger tool for the job if it is labouring continuously.
Heavy orange sparking visible in the vents
Cause: Worn carbon brushes or a damaged commutator on a brushed motor — Fix: On tools with replaceable brushes, that is a cheap fix. On a sealed motor it is usually the end of the tool. Stop using it in the meantime.
Intermittent power, cuts in and out when the lead is moved
Cause: Damaged lead or failing switch — Fix: Take it out of use. A lead damaged internally is a genuine hazard, and rewiring or a switch replacement is a job for someone competent.
Smell of hot plastic, or visible smoke
Cause: Windings or wiring failing — Fix: Stop immediately, remove the battery or unplug, and do not use it again. That smell is insulation failing rather than a motor merely running hot.
Chuck turns but the bit slips
Cause: Worn chuck jaws, not a power problem — Fix: Retighten properly with a hex-shank bit to test. If it still slips, the chuck is worn and replaceable.
Questions people ask
Is a burning smell always serious?
A faint hot-varnish smell from a hard-worked brushed motor is common. Hot plastic, acrid smoke or a smell that persists after cooling is a failing tool and it should not be used again.
Can I replace the carbon brushes myself?
On many mid-range and trade tools, yes — they are behind small caps on the motor housing and are designed to be changed. On budget tools they are often not accessible or not available.
Why is my drill weaker on an extension lead?
Voltage drops along the cable under load, and the drop increases with length and with a coiled reel. The motor sees less voltage and delivers less power.