LG Microwave Error Code F3 – Troubleshooting Guide

Error codes on microwaves can be perplexing. Most microwave owners don’t spend time reading the owner’s manual or learning the various codes for any problem that might crop up. What most do understand is when their microwaves don’t work. 

The LG microwave error code f3 typically pops up when the clock isn’t working or the keypad isn’t functioning. The code tells you that you have a short circuit somewhere in your oven. It could be a sensor, the wiring, the electronic oven control (EOC), or the membrane behind the touchpad. 

Any of those problems will require an inspection and replacement of the failed part. Read the article below to find out how to diagnose your microwave and what you can do to fix it. 

Identifying the Problem

It is important to identify and fix the problem because bad wiring, a faulty sensor, or a non-functioning EOC can start a fire. Most of these types of problems can be fixed by replacing the part, although many home experts will tell you to just go buy another microwave. 

That may be a bad option if you have one of the more expensive versions. 

The problem usually starts with the microwave displaying an f3 code and emitting a constant beeping sound. The clock will zero out and can’t be reset. 

Another problem is the f3 displays at the beginning of a cook cycle or in the middle of a cycle. This stops the cooking cycle. You may reset the microwave to clear the error but it quickly returns. Let’s look at some of the root causes of this problem.

Read: LG Microwave Not Working But Has Power – Troubleshooting Guide

A Bad Sensor

This code is mostly associated with a faulty oven temperature sensor.  You can try to fix the sensor by running a soft reset. Sometimes that works. 

A soft reset is when you put some water and a teaspoon of sugar in a microwavable cup and put it in the microwave on high for 15 to 20 seconds. It can reset the heat sensor and get it working again. 

There are some signs that you have a sensor that is going bad. Some of these include extended cooking times, food coming out undercooked, or cooking unevenly. The microwave may consistently overheat. 

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If the soft reset doesn’t work you can try a hard reset. 

Read: Why LG Microwave Not Heating And Making A Clicking Noise?

What Is a Hard Reset?

You can reset a microwave to clear all the codes and, in essence, start over by resetting the control board. All you have to do is unplug it for about three minutes. Then, plug the appliance back into the power outlet. 

If these quick fixes don’t work, you will either need to replace the sensor or look at possible other problems. 

What is a temperature sensor?

A temperature sensor is something that measures temperature either in the microwave oven or in the room should it be an over-the-range model designed to detect heat from a cooktop. It can also detect liquid temperature, like steam.

The sensor sends messages to the control panel regarding heat and will force the appliance to shut down if it overheats.

Read: How To Reset LG Microwave?

How do I fix the temperature sensor?

Fixing a temperature sensor will require you to do some disassembly of the microwave. You will need some basic tools to do the job. One thing you will need is a multimeter to test the continuity of the sensor once you access it.

The sensor part is officially called a thermistor for the LG microwave. It runs around $25 through most online parts sales places. 

The job of replacing the sensor will involve running a line through your appliance. Even though most experts claim it is a fairly easy fix, the standard advice is to let a professional do it.


Wiring can go bad in a microwave over time and depending on its use. Two wires run from the EOC to the temperature sensor. These may have gotten too hot and burned or become disconnected. 

Unfortunately, this isn’t something you can identify without opening up the rear of the microwave to look at the EOC. That is considered unadvisable unless you know about appliances and fixing microwaves. 

Microwaves hold electrical current in the capacitor even after they are unplugged. A person with little knowledge or skill could become seriously injured or killed with the thousands of volts stored in these appliances. 

This is where it’s best to get a service technician to look at your microwave. 

Read: Why LG Microwave Not Heating Or Turning?

The Electronic Oven Control

The EOC is one of those things that could affect many functions of your microwave if it goes out. It is what keeps your microwave running at a safe, correct temperature. A faulty EOC would cause your appliance to stop working and short-circuit. 

Shorting Membrane Pad

The keypad on a microwave has a membrane behind it that relays messages to the control board for different cooking programs. The membrane is two layers of mylar plastic with a connective coating on the inside of both layers. 

When you press a button, the two layers connect to create a quick current that sends the message to the control board. 

Over time, these mylar layers or the inside coating wear out and that can cause the keypad to short circuit. This will also cause the f3 error. 

However, you will know if it’s your membrane because some buttons may work while others don’t work.

Try resetting the microwave to clear the code and try another program button. You will also know if your keypad is wearing out if you have to press harder to get a function to work. 

Read: How LG Microwave Auto Defrost Works?

Can I fix a membrane issue?

There are online tutorials that explain how to replace the touchpad in a DIY project. Most of the time, this is a safe repair because it doesn’t involve the capacitor. Make sure your microwave is unplugged and do some research before you attempt it.

Here are the steps if you want to replace the membrane yourself. 

First, try resetting the microwave. If that doesn’t work, unplug it again and remove the grill. Now, take out the control panel and find the membrane on the control board. Remove the membrane and replace it. 

Reattach the control board. Put everything back together and plug it in to test it.

How do you test a microwave?

Put water in a microwavable cup and place it in the center of the microwave. Cook on high for one to two minutes. Water should reach the boiling stage at that power and time. 

What is the most likely problem of an f3 error code?

The most common problem resulting in an f3 error code is the keypad membrane has worn out. This is a simple fix that some can do themselves but is relatively inexpensive even with a service tech. 

How much does it cost to get a touchpad replaced?

Most microwave replacement touchpads cost between $100 and $300 to replace, including parts and labor. The exact cost depends on your make, model, and the labor fees set in your area. 

What should I do with my microwave with an f3 error?

You should first try a soft reset, then a hard reset to clear the error. If that doesn’t work, contact the LG support center for more assistance or to find a licensed LG service technician in your area.

Read: LG Microwave Fan Won’t Turn Off – Troubleshooting Guide

Is it worth fixing my microwave with an F3 error?

It may be worth it if you have a more expensive microwave and can find someone to fix it at a reasonable price. Some microwaves cost $400 to $500 now so fixing it with a part for around $100 may be reasonable.

The Danger of the Problem

Those who have a microwave that comes on by itself or does things when you don’t press any buttons has a dangerous short-circuit problem. This could cause a fire. Unplug the machine until you can either get it fixed or buy a new one.

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