Refrigerators and freezers
A fridge that runs but will not cool usually starts with the condenser coils. In city apartments those coils sit under the unit or behind a kick plate, packed with pet hair and dust that make the compressor work twice as hard. Then the tech listens for the evaporator fan behind the freezer wall, since a failed fan keeps the freezer cold while the fridge side warms up. Heavy frost on the evaporator coil points to the defrost system, so the heater, defrost thermostat and control board each get a continuity check with a multimeter. A clicking sound every few minutes with no hum often means a failed start relay or overload on the compressor.
Washers
Standing water in a washer usually traces back to the drain path. The tech clears the pump filter of coins, socks and hair ties, then tests the drain pump motor directly. If the machine will not start or spin, the lid switch on a top-loader or the door lock assembly on a front-loader is a common culprit. Loud banging during spin points to the suspension: worn shock absorbers, springs or a cracked spider arm on the drum.
Dryers
No heat in an electric dryer usually means a blown thermal fuse or a burned-out heating element, and no heat in a gas dryer often means a weak igniter or failed gas valve coils. A drum that will not turn points to a snapped belt, and a squeal or thump points to worn rollers or an idler pulley. Here is the part people skip: a thermal fuse blows for a reason, and that reason is usually a clogged vent. In high-rises with long shared vent runs, the tech will check airflow at the exhaust before calling the job done.
Dishwashers
Water pooling in the tub starts with a check of the filter and drain hose, then the drain pump. If the unit hums but never fills, the water inlet valve and its solenoid get tested. Dishes coming out wet and cold suggest a failed heating element or high-limit thermostat.
Ranges, ovens and cooktops
When a gas oven clicks without lighting, the hot surface igniter has usually weakened and no longer draws enough current to open the safety valve. The tech confirms that with a clamp meter and may check gas pressure at the regulator with a manometer. Electric ovens that heat unevenly often have a broken bake or broil element, and ovens that run hot or cold usually have a drifting temperature sensor, checked against the resistance chart on the tech sheet.
Microwaves
When the light and turntable work but the food stays cold, the magnetron, high-voltage diode or capacitor is a likely suspect. A totally dead microwave often has a blown internal fuse triggered by a bad door switch. Do not open a microwave on your own, because the high-voltage capacitor can hold a lethal charge long after unplugging, and a trained tech discharges it safely before any work begins.
