5 Reasons Your LG Microwave Is Not Heating Food | SOLVED

You may think that the only thing you can do when your LG microwave is not heating food is to buy a new one. However, you may not need to spend money on a new appliance if there’s an easy fix for your problem. Today, I’m going to show you some common issues that may have caused your microwave oven to stop working.

I’m going to show you that some of these problems are simple to solve. There’s absolutely no reason to spend hundreds of dollars on a new microwave oven when you can simply order a replacement part for $20.

Read on to find out the top reasons why your microwave might not be working as well as the solutions to these common problems.

LG Microwave Not Heating Food

I’m going to give you five of the most common reasons why you may not be able to heat up food in your microwave. I’m also going to provide you with tips on how to identify whether a component is not working and let you know how to replace it.

5 Reasons Your LG Microwave Is Not Heating

Below are the five most likely reasons your LG microwave isn’t heating your food. Starting with a burnt-out diode. Work down the list from 1 to 5, as they are in order of the most common causes.

1. Burned Out Diode

If the diode in your microwave oven stops working, it means that the magnetron (a very important component that I’ll talk about later) won’t receive the voltage it requires. This can lead to your microwave not working properly. Most microwave ovens feature diodes that are located close to the high-voltage capacitor.

I must add that not all LG microwaves have the same diodes. In case you’re not sure what type of diode is in your microwave oven, you’ll see the product number and type printed on it.

Replacing a Microwave Diode

It’s easy and cheap to replace a diode in a microwave oven. But first, you must be sure that this component is what’s causing your microwave to not heat up. Diodes generally show visible damage if they’re burned out. You can purchase a new diode here on Amazon.com for around $10.

Check out the short guide below on how to find the diode and replace it:

  1. Open the microwave door and remove the turntable plate and support.
  2. Unscrew the bottom panel of the microwave to locate the diode, which is connected to the high-voltage capacitor.
  3. Check the diode for visible signs of damage, like a blistered spot or a burned crack.
  4. Remove the screw securing the diode and disconnect it from the capacitor terminal.
  5. Find the component number on the diode so that you can order the adequate replacement part.
  6. Install the new diode and make sure you get the right polarity.

Here’s a short video on how to change a diode.

Microwave Isn't Heating? Diode Replacement #W10492278

2. Worn Magnetron 

This is without a doubt one of the most important components of a microwave since it generates heat. After a while, it can become damaged and worn. This is a common problem that can easily be solved with an adequate replacement. You can find replacement magnetrons here from $40 to $60 depending on the model.

Should You Replace a Worn Magnetron?

I’d advise you to get the worn magnetron replaced if your microwave oven is relatively new and under warranty, as you’ll be covered for the repair. However, if you’ve been using it for more than five years, you should probably buy a new microwave. It’s only a matter of time before other components start breaking down after being in use for years.

Before you consider replacing it, you should first check whether this component is what’s actually causing the problem. Here’s how you can find the magnetron in your microwave and test it for continuity:

  1. Locate the magnetron by first unscrewing the casing from each side of your microwave oven.
  2. Once you remove the casing, you’ll see a component near the back of the microwave that looks like two metal boxes stacked on top of each other.
  3. Unscrew the magnetron and pull it out of the microwave.
  4. Now grab your multimeter and set it to the lowest ohm setting.
  5. Connect the leads of the multimeter to the magnetron terminals.
  6. You should be getting a reading below 1 ohm if the magnetron is working, but there’s still one more test to do.
  7. Set your multimeter to the highest ohm setting and place a lead against the metal casing of the magnetron, while placing the other lead on the metal box.
  8. If you get a reading that shows “Open Line” or “OL”, your magnetron is working properly.

If you want to know more about replacing a magnetron, you can check the video below.

Checking and Replacing Magnetron in a Microwave. ( Runs but no heat )

3. Faulty Door Switches

One of the most common reasons why your LG microwave is not heating up is due to a faulty door switch. There is a safety measure put in place in every single microwave oven that prevents the appliance from running in case the door is open. This is an important mechanism because the radiation that is generated in microwave ovens can cause burns on human skin.

How to Replace a Faulty Door Switch

To replace this component, you’ll first need to order a replacement microwave oven door switch. Regardless of the model of your appliance, a door switch shouldn’t cost more than $25, at here Appliance Parts Pro you can buy them for around $10. After the replacement arrives, you’ll need to unplug your microwave and wait at least 15 minutes for the components to discharge.

  1. Remove the screws on top of the microwave. You have to do this so you can loosen and remove the grill. 
  2. Then, simply remove the control panel and the faulty door switch by removing the screws attached to these parts. 
  3. Place the new door switch where the old one was and reassemble the microwave. 

That’s it. You’ll only need several minutes to finish the whole process.

4. Faulty High-Voltage Transformer

The high-voltage transformer in your microwave oven powers the magnetron. If you suddenly can’t heat up your food anymore, it might be due to a faulty transformer. When this component starts malfunctioning, you may notice a burning smell. There’s also a possibility you’ll see sparks of electricity being produced by the transformer. This is a sign you should immediately stop using the microwave and replace the transformer.

high voltage transformer
Buy replacement OE transformer

How to Troubleshoot the High-Voltage Transformer

Regardless of whether you see sparks of electricity coming from the transformer or not, you should immediately unplug your microwave oven and let it sit for a while so that all components get discharged. Afterward, you can check whether the transformer is actually causing the microwave to malfunction. Start by disconnecting it from the power source.

You’ll also need a voltmeter or a multimeter. Use the ohm setting to test the terminals of the transformer. When it’s working properly, this component should show resistance of between 50 and 70 ohms. In case you get values in a different range, it means your transformer is not working properly and should be replaced.

5. Faulty High-Voltage Capacitor

The capacitor provides the magnetron with the high voltage that it needs to work properly. When you plug in your microwave oven, it can only receive the power of 120 volts from the wall socket. The capacitor transforms this power with the help of its diode and turns it into the high voltage the magnetron requires to heat food. Like any component of the microwave, the capacitor also has an expiration date and may break down.

How to Test a High-Voltage Capacitor

In case you know your way around appliances, it shouldn’t be a problem for you to test or even replace a high-voltage capacitor. It will certainly save you the time and money required to hire a professional repair person to do it. However, if you’re not that handy around appliances, it might be best to leave it to the professionals because testing and replacing a capacitor can be quite dangerous for people who’re not 100% sure what they’re doing.

To test this component, you’ll need a voltmeter or a multimeter that you’ll set to the ohm mode. Before you do anything, make sure the microwave is not plugged in and give the components time to discharge (at least 15 minutes). Set the voltmeter/multimeter to 1,000 ohms and connect it to the capacitor terminals. If you get zero ohms as the value from the readings, it means your capacitor is not working. You can find an LG replacement capacitor here.

Microwave Not Heating Squealing When Running

It’s easier to pinpoint exactly what the problem is with your microwave if you notice other symptoms. For instance, if your LG microwave is not heating and you also notice a squealing noise coming from it, you’ll know that either the diode or the magnetron is causing the problem.

Worn Magnetron or Diode

Sometimes, it will be easy for you to spot that a diode or magnetron is faulty. As I already mentioned, hearing squealing noises coming from the appliance is a common sign. There are also a few other signs you should watch out for. One is a burning smell that you’ll surely notice when either of these two components stops working. There’s also the possibility of hearing a loud clicking sound, which is a sign your magnetron has stopped working.

The Turntable is Not Working And Microwave is Not Heating

Today, you already learned that when your microwave oven isn’t heating up food, it can be due to at least five different reasons. Now couple that problem with the fact that the turntable is not moving and it’ll be easy for you to determine exactly what the problem is.

Turntable Motor Faulty

The turntable motor is just like any other component of the microwave oven, meaning that it stops working after being in use for some time. Sometimes, it’s easy to spot problems with the turntable motor before it stops spinning completely. For example, you may notice that the turntable has slowed down in speed significantly. This is already a sign that the motor should be replaced soon. Affordable replacement turntable motors are available here for $25.

Fixing A LG Microwave That Is Not Heating

There are two options when it comes to fixing a microwave. You can either do it yourself or get in touch with a professional repair technician. Although it’s cheaper to do it yourself, you shouldn’t attempt to do this in case you don’t have any experience with fixing appliances. I’m saying this for your safety.

Is Your Microwave Still Under Warranty

In case your microwave oven is still under warranty, then it’s a no-brainer. You shouldn’t fix it yourself even if you know how to. Instead, you should get in touch with the company and ask for a replacement or free repair, which you’re entitled to when the product you own is still under warranty.

Cost to Fix Vs Buying A New Microwave

The average component you’ll need to replace if your microwave is not heating up likely won’t cost a lot of money. I’m all for people finding a cheap way to fix one of their favorite appliances. 

But I also have to mention that if it’s been years since you bought the microwave oven that’s now not working properly, you might want to buy a new one. Even if you replace one component in a microwave you’ve been using for more than five years, there’s a good chance another component will start malfunctioning soon.

That’s why I recommend buying a new microwave if you’ve been using the one you have now for several years.

LG Microwave Not Heating – Solved

When your LG microwave is not heating food, it could be due to one of several reasons. In most cases, it’s either a worn magnetron or a faulty door switch. However, it can also be due to a burned-out diode, faulty transformer, or a malfunctioning capacitor. 

Whatever the case may be, you can easily identify and replace the faulty component if you know your way around appliances. If not, it’s best to contact a professional repair person.

Andrew Brown
Appliance Service Technician | Website

Andy has over 8 years of experience working on residential household appliances, performing diagnostics, and repairs across most major brands. He graduated from the Denver Institute of Technology, is NASTeC certified, and has worked for Mr. Appliance. Andy has contributed to features on major publications including Better Home & Gardens, Family Handyman, and Yahoo.com.