How do I fix a power tool that has stopped working?

Most dead power tools have one of four faults, none of which is the motor, and three of which can be fixed for a few pounds. Working inwards from the socket finds them quickly.

Safety

Step by step

1. Start at the power source.Test the socket with something else, check the RCD and the fuse in the plug. It sounds too obvious and it is the fault often enough to be worth thirty seconds.
2. Flex the cable and look at both ends.Cables break internally at the strain relief where they leave the tool and at the plug. Flexing while it is running — if it runs intermittently — will show it, and it is a common and easy repair.
3. Check the battery and its contacts on cordless.Try another battery and another charger. Clean the contacts on both battery and tool. Lithium packs also enter a protection state that a proper charger will reset.
4. Look at the brushes on a corded tool.Carbon brushes wear out and are the most common failure in older corded tools. They are usually behind two accessible caps on the motor housing, cost a few pounds, and take ten minutes to replace.
5. Know the signs of worn brushes.Excessive sparking at the motor, loss of power, intermittent running, or a tool that starts when tapped. Replace them in pairs and check the spring is intact.
6. Test the switch.Switches fill with dust and fail, particularly on sanders and saws. Continuity across it with a meter, unplugged, tells you immediately. Replacements are usually available and cheap.
7. Check the thermal cut-out.Many tools shut down when hot and reset after twenty minutes. A tool that dies during heavy use and works again later is doing exactly this, and it is telling you to work it less hard.
8. Look for a mechanical jam.If the motor hums but nothing turns, something is seized. Clear debris, check the gearbox and the chuck, and never keep powering a stalled motor — that is what burns out windings.
9. Clean out the dust.Compressed air through the vents. Dust packed around a motor causes overheating and is a genuine cause of failure in sanders and routers.
10. Recognise a burnt-out motor.A sharp burning smell, blackened windings, or a tool that trips the RCD. That is the end of a cheap tool and a professional repair on an expensive one.
11. Look for spare parts before giving up.Brushes, switches, cables, chucks and gears are widely available for most brands. Model number and an exploded diagram from the manufacturer's site is usually enough.
12. Weigh the repair against replacement.Brushes or a switch on any tool, yes. An armature or a gearbox on a budget tool, no. Consider the safety of a repaired mains tool as part of that.
13. Dispose of it properly if it is finished.Electrical waste and batteries have to be recycled, not binned. Retailers and household waste sites both take them.

Tips

• Carbon brushes first on any older corded tool that has lost power or runs intermittently. It is the most common failure and the cheapest fix.
• Sparking at the motor is a diagnosis, not just an appearance. A lot of it means the brushes are near the end.
• A tool that works again after cooling down has a thermal cut-out doing its job. It is a warning about how it is being used, not a fault.

Common mistakes

• Continuing to power a stalled motor — The windings overheat within seconds and burn out, turning a jam into a scrapped tool.
• Testing a tool with the casing open and plugged in — Exposed mains connections. Always diagnose unplugged, with a meter, and reassemble before testing.

If it doesn't work

Questions people ask