---
title: "Microwave repair"
description: "LG microwave repair — built-in and over-the-range machines, where the value is in the installation as much as the appliance."
url: "https://lgmiami.support/services/microwave-repair/"
date_modified: "2026-09-06"
Appliance type: "Microwaves"
---


# LG microwave repair

### The cup of water test, and the one thing not to open

If you are not sure whether it is heating, put a mug of cold water inside and run it for a minute. Water that comes out barely warm points at the high-voltage side rather than the turntable or the controls. That is also the point at which to stop. A microwave holds a charge in its capacitor long after it has been unplugged, big enough to be genuinely dangerous, and it is the one appliance in the kitchen we ask people not to open. If it runs with the door open, sparks inside, or has begun to hum far louder than it used to, unplug it and leave it for us.

What this involves

A machine that runs and does not heat is the magnetron circuit, specifically

A door interlock that has failed is a safety repair and comes out of service today

The capacitor holds a lethal charge — this is the one appliance not to open

Run the one-cup test

A minute, a mug and cold water settles whether it is producing power at all.

Test the interlock chain

Three switches that must agree. A machine that starts on its own has lost part of it.

Discharge before anything else

The capacitor is discharged as the first step of any internal work, every time.

Diagnose the high voltage circuit

Magnetron, diode, capacitor and transformer produce the same symptom and cost differently.

Be honest about the economics

On a countertop machine we will say when a new one is the better answer.

### It sparks when I run it.

Unplug it. Usually it is the waveguide cover on the inside wall, a small consumable part that chars and then arcs, though it can be what sits behind it. Either way, running the machine in that state damages it further.

### The turntable spins but nothing gets hot.

The controls and the motor are healthy and the magnetron circuit is not. On a built-in or over-the-range machine that is worth diagnosing; on a countertop one we will tell you plainly when a new machine costs less.

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**[Read full article: Microwave repair](https://lgmiami.support/services/microwave-repair/)**