Domestic and Industrial Appliance Repair
Scope
This domain tests fault diagnosis and repair of ceiling fans, mixers, washing machines, refrigerators, geysers, irons and small industrial appliances.
Core rules
- Ceiling fan: capacitor-run motor; a 2.25 µF, 440 V AC capacitor is common. Weak capacitor gives low speed and hum; open capacitor gives no start. Check winding resistance and bearing condition before replacing the capacitor.
- Mixer grinder: universal motor with carbon brushes; sparking, weak torque and noise point to worn brushes, commutator burning or a shorted field coil.
- Refrigerator: compressor has run, start and common terminals; run winding resistance is lower than start winding. PTC relay and overload protector are common failure points; never open a sealed compressor system without recovery equipment.
- Geyser and iron: element and thermostat faults; test element continuity and insulation resistance to earth.
- Washing machine: inlet valve, timer/PCB, motor capacitor and door interlock are the usual suspects.
Worked example
A 1,500 W geyser at 230 V should draw I = P/V = 6.52 A and have an element resistance R = V²/P = 230²/1,500 = 35.3 Ω. A reading of infinity means the element is open; a reading near zero means it is shorted; a reading of 35 Ω but no heating suggests the thermostat or supply is at fault. An insulation test from element to earth should read above 1 MΩ - anything lower is a shock risk and the element must be replaced.
Traps that cost marks
Fitting a capacitor of the wrong microfarad or voltage rating, discharging a microwave high-voltage capacitor by hand, and condemning a compressor before checking the PTC relay and overload. Always unplug before dismantling.