Refrigerators and freezers
When a refrigerator runs without cooling, the condenser coils are usually the first stop. In apartments, those coils hide underneath or behind the toe grille, matted with dust and pet hair that force the compressor to overwork. Next the tech listens for the evaporator fan behind the freezer panel, because a dead fan leaves a freezer cold and the fresh food side warm. 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. Repeated clicking with no compressor hum often means the start relay or overload has failed.
Washers
A washer full of standing water almost always comes down to the drain path. The tech checks the pump filter for socks, coins and hair ties, then tests the drain pump motor itself. 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 sits still suggests a broken belt, while squealing or thumping points to worn drum rollers or the 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 tech tests the water inlet valve and its solenoid. Dishes that come out cold and wet usually mean a failed heating element or high-limit thermostat.
Ranges, ovens and cooktops
A gas oven that clicks but will not light usually has a weak hot surface igniter that no longer pulls enough current to open the safety valve. The tech checks that with a clamp meter, and may use a manometer to confirm gas pressure at the regulator. Electric ovens that heat unevenly often have a split bake or broil element, and an oven that runs hot or cold usually has a drifting temperature sensor tested against the tech sheet resistance chart.
Microwaves
If the light and turntable work but food stays cold, the magnetron, high-voltage diode or capacitor may be at fault. 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.
