Why Microwave Light and Fan Stay On? – Troubleshooting Guide

It can be an aggravating thing for a microwave to suddenly have issues. One of those that can be an annoyance is if the microwave light and fan stay on long after they should be off. It is fortunate that this problem isn’t a dangerous one and can be easily fixed 

There are two reasons for the light and fan to keep running in a microwave. It is either faulty door switches or it could be the control panel. The door assembly, like a broken latch, could also be to blame. The most common reason for this problem is faulty door switches. 

Read further to figure out how to fix the problem and what you need to do to replace the switches. 

How the Door Switch Works?

All microwaves are built today for the door interlocking switch to connect once the door latch works. It activates the door switch. The switch in the door provides relays to other components to start power for things like the light, heat, and fan. 

A switch that is stuck or not working will sometimes stick in the position to push power to components even whether the door is opened or closed or whether the oven is turned on or not. 

One thing to know is that microwaves actually have three door switches. They all serve different functions and it is usually the lower one that functions things like the fan and cooking. 

Each door switch is typically black with a small metal actuator on the top. They have either two or three terminals but most have three. The terminals are the common, the open, and the closed terminals. Those door switches that have two terminals have a common and either an open or a closed terminal. 

These facts are important to know for understanding how to test the switches, which you will need to do if you plan on replacing them.

Read: How To Vent A Microwave On An Interior Wall

The Door Latch

The door hook or late is located inside the cabinet. It is a small plastic piece that can break over time. It can also be replaced in a DIY project. 

If the problem is with the control panel, it’s best to call a professional.

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Read: Microwave Blown Fuse Symptoms

What to Do First?

There are a couple of quick fixes that may fix your microwave. They are worth a shot to try before you start disassembling to get to the door switches. 

First, try opening and slamming the microwave door 10 times. This is a way many support center staffers say will reset your microwave. Some have reported it working and fixing the problem. Sometimes, this could work if the door switch is just sticking. 

The second thing to do is to clean the door switches. Grease, grime, and old food can get stuck in several odd places in a microwave and that can cause the door switches to stick. A sponge, mild soap, and water will go a long way to possibly solving your problem.

You’ll have to test the switch if those methods do nothing.

Read: Top Reasons Why Microwave Is Not Heating

Removing the Switch

You will need to take out the door switches to test them. First, disconnect your microwave from the power outlet. 

Now, you will need to remove the microwave’s cabinet to access the door switches. To find the door switches, open the door and remove the screws that hold the grill. Move and release the grill. 

Now you will see the control panel with a screw to the left holding it. Take out that screw. Loosen the screw located behind the control panel. Detach the panel. You will need to lift and pull it forward to detach it.

You will need to remove the screws that hold the switch assembly in place. after that, press the release tab and the actuator. The switch should detach. Disconnect the wire to release the switch.

Testing the Door Switch

Door switches may look different, depending on the model, but they all have at least two to three terminals. All are tested the same way with a multimeter, or voltmeter.

To do that:

  1. Set the multimeter to Rx1.
  2. Make sure the button is pushed in.
  3. Touch the terminals with the meter’s probes. The black probe goes on the common terminal and the other probe typically goes on the open terminal if there are three terminals. Otherwise, put it on the second terminal.
  4. The reading should be zero or close to it to show continuity.
  5. Keep the probes on the terminals but make sure the button isn’t depressed. Your multimeter should show there isn’t continuity. 

This would indicate the switch is working. If you get different test results, then you have a faulty door switch and will need to replace it.

Read: 5 Possible Issues When Microwave Turntable Is Not Turning

Replacing the Switch

Replacing a door switch is fairly simple. You are just reversing what you just did to take it out.

Attach it to the wire connector first. Then, put the new switch in and snap it. Put it in the frame so the screws you took out can go back in. 

Return the control panel and tighten the screw that goes behind it. Put the screw from the left side back in and put the grill back into place. Tighten screws to secure the grill. That’s it. 

Now just plug the microwave back in and test it to see if it works.

Should You Replace All Switches?

Most appliance and service center technicians advise you to go ahead and replace all three door switches since you are replacing one. Typically, they all last about the same amount of time so either of the other two could go out at any time.

That would mean you would have to disassemble the microwave again and no one wants to do that. The switches are cheap enough that it would be easier to just replace them all at once. 

How Much Do Door Switches Cost?

The standard switches will run about $40 for most microwaves if you get them from the company or service dealer. However, you can buy many brands on Amazon for $10 or less. 

A Caution

There is one caution about working on microwaves and that’s the capacitor. You shouldn’t be around the capacity to fix a door switch but it should be discharged before you try to repair any of the internal components. 

The capacity holds a strong electrical current, up to 4,000 volts, and can send a shock even after the appliance is unplugged. That could result in serious injury or death.

Read: 5 Reasons Why Microwave Is Sparking Inside

Testing a Microwave

You would think you could just heat food in it to test it but that isn’t the way it’s done. Testing a microwave involves two large cups of water at normal temperature. Put the cups in the microwave and heat for two minutes. 

The water should be boiling in both cups. If the temperature is off in one cup or if the water isn’t hot enough, you have another problem.

Is it normal for my fan to keep running?

The microwave’s exhaust fan will continue to run after you are finished cooking on your stove.

This is an automatic function and the fan will turn off when the kitchen temperature is closer to normal. The exhaust fan is turned on when it senses heat rising in the kitchen while you are cooking. Typically, it takes about 30 minutes for the temperature to cool down and the fan to cut off.

How do I turn off a microwave vent?

You can turn off the microwave’s vent by pressing the button called “control setup” or “options.” The microwave will enter a setup mode. 

Scroll until you see “vent fan” as a sub-menu. Push the enter or start button.

Now, press the off button and push the enter or start button a second time. The vent fan is now turned off.

Resetting a Microwave

Sometimes, microwaves will send an error code if something like the fan isn’t working correctly. You can reset the microwave and clear the error code by unplugging it, waiting about a minute, and plugging it back into the wall outlet.

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