Microwave Repair in Philadelphia

The part of a microwave that heats food is a magnetron, a tube that generates microwave energy when it is fed several thousand volts. A transformer and a high-voltage capacitor build that voltage. The capacitor can keep a dangerous charge long after the microwave has been unplugged, which is why opening the outer cabinet is not a do-it-yourself job, even for someone handy with other appliances.

Around that high-voltage section are ordinary parts: a door with several interlock switches, a turntable motor, a light, a cooling fan, a thermal cutoff, a control board and a keypad. Many common microwave problems are actually in this lower-voltage group, and the symptom usually tells which group to look at first.

Runs, light on, turntable spins, food stays cold: the classic sign of a high-voltage fault. The magnetron, high-voltage diode, capacitor or transformer has failed, or a thermal cutoff on the magnetron has opened. A buzzing or humming that is louder than usual often comes with it.

Completely dead, no display: a blown internal fuse, frequently caused by a door interlock switch that has failed and shorted. When the fuse blows, the interlock switches have to be checked too, or the new fuse will blow again.

Starts and stops randomly, or will not start with the door closed: door interlock switches or a misaligned door. A door that has been slammed for years or a cracked latch hook is a common root cause.

Sparks inside: metal in the cavity, a damaged waveguide cover, or chipped paint inside the cavity exposing bare metal. Stop using it until it is inspected; continuous arcing can damage the magnetron.

Keypad unresponsive or pressing itself: a worn membrane keypad, often from steam or cleaning spray getting behind it, or a control board fault.

Turntable not turning, but the food still heats: the turntable motor under the floor of the cavity, or a coupler that has cracked. Food heating unevenly on a model without a turntable usually points to the stirrer that spreads the energy around the cavity.

An over-the-range microwave also serves as the kitchen's range hood. It has an exhaust fan, a light for the cooktop below, and grease filters on the underside. Some vent outdoors through a wall or the ceiling; many in apartments and condos recirculate air through a charcoal filter instead.

That dual role adds failure points. The vent fan motor can wear out or get gummed with grease, the cooktop light can fail, and a heat sensor may switch the fan on automatically when the burners below run hot, which is normal. Clean the grease filters every month or two and replace charcoal filters as the manufacturer suggests. Grease that gets past a saturated filter strains the fan motor and coats the electronics.

Removing an over-the-range unit for repair is a two-person job. It hangs on a wall plate and bolts through the cabinet above, and its weight has to be supported throughout.

Built-in microwaves, microwave drawers and over-the-range models are standard in many Center City condos, high-rise apartments and newer rowhomes. In a high-rise, a repair that may involve carrying a unit in or out can require a freight-elevator reservation and building approval for contractors. Check with your building management before the visit about their requirements for service technicians, so the day runs smoothly.

In older homes, a microwave sometimes shares a kitchen circuit with a toaster, coffee maker or refrigerator, and a microwave that trips a breaker the moment it starts may be overloading a shared circuit rather than failing. Two-prong ungrounded outlets are also still found in some older Philadelphia houses. A microwave should be plugged into a properly grounded outlet; an adapter is not a substitute, and an electrician is the right person to fix the outlet.

Steam and humidity are hard on keypads and control boards. In a small rowhouse kitchen with a pot boiling on the cooktop below and summer humidity on top of that, running the vent fan while cooking helps keep moisture out of the microwave's electronics.

Before anything else, the technician safely discharges the high-voltage capacitor. Then the parts are tested in turn: fuse, door interlocks, thermal cutoffs, transformer windings, diode, capacitor and magnetron. The door is checked for alignment and the cavity for damage. Testing usually takes less time than removing an over-the-range unit from the wall, if that is needed.

The repair goes ahead only after you have seen and approved the written price. Common repairs include fuses with interlock switches, the high-voltage diode, turntable motors, vent fan motors, lights, door parts and keypads.

For over-the-range models, the vent fan, the cooktop light and the grease filters get a look as well, since they are often the real reason someone calls. If the unit has to come off the wall, the mounting plate and the bolts through the upper cabinet are checked when it goes back up, so the microwave is secure.

For a basic countertop microwave, replacement is often the sensible choice once the magnetron or control board fails, since the parts and labor can come close to what a new one costs. We will say so rather than push a repair.

Over-the-range, built-in and drawer microwaves are different. They cost more, they are fitted to the cabinetry, and replacing them involves installation work. For those, magnetrons, boards, interlocks and fans are usually worth repairing, especially on a unit that otherwise matches a kitchen's other appliances.