This is the one category where we frequently talk customers out of a repair, and it is worth explaining why, because the reasoning is entirely about what the appliance is bolted into.
The fault is usually one of three parts
A microwave that runs, lights up and turns the plate but does not heat has almost always lost something in the high-voltage circuit: the magnetron, the high-voltage diode, or the capacitor. A door interlock switch can also prevent heating, and that one is inexpensive.
Diagnosis is quick for a technician with the right meter. The economics afterwards are what matter.
Countertop units: usually replace
A magnetron plus labor on a countertop microwave often approaches or exceeds the price of a new one of similar capacity. We will diagnose it, tell you what it needs, charge the diagnostic, and recommend replacement in most cases. That is not us avoiding work — it is the arithmetic, and you would reach the same conclusion with the same numbers.
The exception is a high-end countertop unit — inverter models, convection combinations, commercial-grade boxes — where the replacement cost is high enough that repair makes sense again.
Built-in and over-the-range units: usually repair
This is the other side. A built-in microwave or a microwave-oven combination is sized to a specific cabinet cut-out and trim kit. An over-the-range unit is matched to the range and the cabinet above it. Replacing either is not a $200 decision — it is an appliance plus, frequently, cabinet modification.
At that point a magnetron, a diode, a door switch assembly or a control board is clearly worth doing. Typical built-in repairs land between $240 and $420 with parts and labor, against a replacement cost that starts several times higher once installation is counted.
The one genuine safety warning in this article
Do not open a microwave cabinet. The high-voltage capacitor can hold a lethal charge after the unit is unplugged, and it does not need to be plugged in to hurt you. Of all common appliance repairs, this is the one where DIY carries a real risk of death rather than a risk of a wasted afternoon. Discharging that capacitor safely requires knowing exactly what you are doing.
Everything else in this blog is fair game for a careful owner. This is not.
Faults worth checking before you write it off
- •Turntable not turning, otherwise heating fine — a small motor, cheap fix.
- •Buttons unresponsive or intermittent — membrane keypad or control board; on a built-in, worth doing.
- •Sparking inside — usually a burnt waveguide cover, a genuinely inexpensive part. Stop using it until it is replaced.
- •Loud vibration from an over-the-range unit — the vent fan blower, not the microwave circuit.
- •Door not latching — interlock and latch assembly; the unit is designed to refuse to heat, which is correct behaviour.
What to expect from us
We will tell you plainly which side of the line your machine is on. If it is a five-year-old countertop unit needing a magnetron, we are going to recommend you spend the money on a new one and we will only charge the diagnostic. If it is a built-in behind a trim kit, we will fix it and it will be the cheaper choice by a wide margin.