LG Microwave Fan Won’t Turn Off – Troubleshooting Guide

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A microwave fan can sometimes give you problems. One of those problems is that sometimes the fan won’t go off. This can cause some aggravation. Yet, there are things you can do about it. 

There are a couple of common answers for when an LG microwave fan won’t turn off. The most common problem is something is wrong with the oven control board. It could also be a problem with the high limit thermostat or a regular thermostat. It could also be the on-off switch, door switches, or the fan itself.

The Automatic Vent Fan

The automatic vent fan is in LG Over-The-Range microwave ovens. This is a built-in feature where the fan automatically comes on to move heat away from your stove. It is a really effective fan for the hood and usually works well 

It works when the microwave oven senses heat from the cooktop that increases the temperature. It then turns on the vent fan for you to cool down the room. The feature only operates the fan and doesn’t turn on your microwave for cooking. 

You may see a display showing you the fan is activated but that isn’t on all models. Microwaves with standard LED displays do not show when the fan is operating. Those LG models with scrolling text displays will show you the surface below is hot. 

A key point about this type of vent fan system is you can’t manually shut off the fan. The fan will stop when it senses the surface below is back to a normal, safe temperature. It can run up to 30 minutes after cooking has stopped and the stove is turned off.

Read: How To Vent A Microwave On An Interior Wall

When to Worry?

The time to grow concerned over the fan running is when it simply won’t stop even after the cooking time is long over. You should also know a countertop microwave shouldn’t have a fan running for a long time after you’ve taken your food out. 

There is probably something failed in your appliance if you notice the microwave fan constantly running even when you aren’t cooking anything. 

The most common problem when an LG product has fan issues, whether it’s a microwave or range oven, is in the oven control board. The board relays information to control fan circuits according to what the sensors message it to do as well as the user settings. 

When there is a short-circuited relay, the board sends out constant voltage to the fan. While this is the most common problem, it is also the most expensive to fix. So, it’s best to check out other possible causes first.

Read: Microwave Blown Fuse Symptoms

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Thermostats

Your oven may have a high-limit thermostat or a regular thermostat. While they are two different types, the problem ends up being basically the same. 

A defective high-limit thermostat will keep sending electricity to the fan even if the temperature has cooled. You would need to test it with a multimeter to check continuity. If it doesn’t have continuity, replace it.

A thermostat also sends electricity to the van as the microwave heats. It could be stuck or closed and that will cause it to continue to send voltage even if the oven has cooled. 

Again, you will need to use a multimeter to check the thermostat’s continuity. It is defective if it shows continuity regardless of temperature.

Read: Top Reasons Why Microwave Is Not Heating

Fan

The fan motor could be the issue. Checking it with a multimeter would involve taking the microwave out and disassembling it some. That may be above many people’s skill or comfort level. Even so, it would need to be checked for continuity. 

A new fan motor isn’t expensive and isn’t hard to put in but you do have to have some skills to do it. 

On/Off Button

There are times when the fan problem is because the microwave’s on-off switch isn’t functioning correctly. It could be sticking or not engaging at all. Usually, this prevents other problems too like the microwave from cooking. 

However, if it’s the on-off switch that is giving you problems, you will need to have a service technician remove the whole control panel to replace it.

Door Sensors

One of the oddest problems contributing to fan issues is door sensors. Yet, these may be the simplest things to fix and really should probably be the first thing you try before digging into your microwave’s innards. 

In fact, LG customer service tells people with continuously running fans to open and slam the door 10 times. Many said it worked because it reset the switches. Others said the fan problem was resolved once they replaced the switches. 

Another LG microwave customer said they reset the breaker and that resolved the fan issue.

You may try to clean the door sensors. Sometimes, door sensors accumulate dirt and grime that prevent them from working effectively. Cleaning them with a sponge, mild soap and water could get them unstuck and working better. 

Read: 5 Possible Issues When Microwave Turntable Is Not Turning

What Do Door Sensors Have to Do With Fans?

Microwave ovens today have many parts interconnected to other parts. Each of these parts, like a door sensor, relays messages to other parts like fans. The door sensor tells the rest of the oven that it’s safe to cook and also has some control over relaying temperature. 

The fan runs when it senses there is an increase in temperature or while something is cooking so it’s all related.

Can you shut off a fan manually?

LG states you can’t turn off an automatic fan when it’s running. However, some appliance gurus state you can turn it off by pressing the button labeled “fan” until it indicates it’s off in the display. 

You can also simply unplug the microwave to shut off the fan but this is only a temporary solution.

There isn’t any guarantee it will remain off when you plug it back in unless the temperature has cooled down. One thing you could do to speed up the process of the fan shutting off is to open the microwave door. That allows the microwave to cool down quicker. 

Why does my microwave fan come on when I open the door?

This could be a safety issue. The root of this problem is typically a faulty switch in the door. The switch tells the control board when the door is closed or open and that turns the microwave on and off, as well as the fan. 

Inspect the door switches and replace them if necessary. 

Why did my microwave fan stop working?

An automatic microwave fan will shut off when the temperatures are back to normal after cooking. However, if the fan doesn’t come on at all, it could be that the grease filter is clogged. 

This is a filter that takes in fats and oils that develop when food is heated. It traps them so they don’t go through the exhaust system. It’s typical for filters to get gunk in them over time, requiring cleaning or replacing.

How do I know if my microwave vent is working?

Your microwave vent is designed to push hot air outside. Go outside and find the wall cap around the kitchen exterior wall. The wall cap is where the air escapes from the kitchen vent. Check to see if the air is coming out of it while the fan is running.

Read: 5 Reasons Why Microwave Is Sparking Inside

What happens if a microwave isn’t properly vented?

Any microwave needs proper airflow to work correctly. An appliance that isn’t properly vented will start malfunctioning and won’t be as efficient.

Keeping Your Microwave Clean

One of the most important things you can do to keep your microwave running well for years is to keep it clean. Wipe it out regularly and check it for food and other debris, especially in the vents or under a turntable. 

Cleaning also means checking the door latch assembly for stray and hardened food, wiping down the door and door sensors, and making sure food doesn’t get into any of the crevices.

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