Judging based on the appearance
| Fault condition | Possible causes | Warranty/No warranty |
| The tool has been disassembled | Caused by improper operation | No |
| The tool has been opened, causing further damage | Caused by improper operation | No |
| Casing is cracked | Dropped or crushed | No |
| Cable or plug is damaged | Caused by improper operation | No |
| Output shaft is deformed or bent | Severe impact from external forces | No |
| Appearance is dirty (the interior is also) | Not following operational requirements (such as foreign objects entering) Following operational requirements | No/Yes |
| Base plate is damaged or bent (for jigsaws, circular saws, stone cutting machines, sanders, edgers, and routers) | Dropped or crushed Caused by improper operation | No |
| Sandpaper machine base pad | Natural wear and tear during use | No |
| Guard is deformed (for angle grinders, circular, and cutting machines) | Dropped, hit, or crushed | No |
| Damage traces caused by flames | Contact with fire source | No |
| Plastic casing or aluminum parts are worn | Natural wear and tear during use | No |
| External wear parts such as drill chucks, flanges, sandpaper clamps, etc. | Natural wear and tear during use | No |
| Drill chuck is jammed | Drill bit is vertical or diameter deviation | No |
| All accessories and auxiliary parts included with the tool are damaged, such as saw blades, wrenches, batteries, drill bits, auxiliary handles, etc. | No |
Judging Based on Internal Conditions
| Fault Condition | Possible Cause | Warranty/No Warranty |
| 1. Rotor and stator are fused together (burned out) | Overload | No |
| 2. Rotor or stator is damaged but with the same discoloration | Ventilation passage blocked | No |
| 3. Rotor commutator segments are lifted or swollen, and the rotor winding is not short-circuited | Original quality of the commutator | Yes |
| 4. Rotor winding short-circuited, stator winding is intact or only slightly discolored | Winding or grounding short-circuited with the rotor Removed carbon brush self-disconnect protection device and continued to use | Yes/No |
| 5. Rotor is damaged | Winding short-circuited | Yes |
| 6. Rotor is normal, stator’s two windings are discolored to varying degrees; or one is charred or discolored, the other is intact | Caused by vibration Obvious manual disassembly and impact | Yes No |
| 7. Stator or rotor commutator contact point is broken | Improper assembly or manufacturing defect | Yes |
| 8. Gear wear of the shaft or large and small bevel gears | Normal wear or lack of regular maintenance | No |
| 9. Guard is deformed (for angle grinders, circular saws, cutting machines) | End of normal lifespan | No |
| 10. Switch, electronic circuit board is damaged | Leakage of oil or lubricating oil drying out | Yes |
| 11. Abnormal sound or damage in the transmission mechanism | Lack of maintenance | No |
| 12. Commutator wear marks exceed 0.2MM on one side | End of service life | No |
| 13. Damage to carbon brushes, bearings, shaft sleeves, O-rings (seals), cylinders, pistons, impactors, etc. | End of service life | No |
Other Conditions
| Fault Condition | Possible Cause | Warranty/No Warranty |
| 1. Lithium battery does not discharge | Caused by improper operation | Yes |
| 2. Short discharge time of lithium battery | Natural consumption with the number of charge and discharge cycles, if the fault battery’s no-load discharge time after full charge is below 60% of the new battery’s no-load discharge time Natural consumption with the number of charge and discharge cycles, if the fault battery’s no-load discharge time after full charge is above 60% of the new battery’s no-load discharge time | Yes/No |
| 3. Charger does not charge | Component damage | Yes |
| 4. Heat gun does not heat up | Heating element brokenAutomatic thermostat faulty | No/Yes |