In terms of microwave malfunction, having the light go out inside the microwave cabinet is not exactly a huge problem. It doesn’t so much prevent you from using the appliance so much as it prevents you from covertly heating up a burrito at midnight in a dark house. Regardless, it is nice to be able to use your microwave without turning on other lights. The light inside can also help you more accurately judge how well heated up your food is.
As for what caused this. There are obvious causes that prevent a light in your microwave from working, and there are some less obvious causes. If the less obvious causes are responsible, it will not be long before you start having bigger problems with this appliance. As such, here is what you need to check and replace to get your microwave back to 100 percent function.
The Light Bulb Has Burnt Out
If the light in your microwave is faulty, the most obvious culprit is the light bulb itself. The good news is that if it is indeed the light bulb, it is also the easiest fix for this issue. To diagnose concretely if this is your problem, all you need to do is replace the light bulb. A burnt out bulb can be common if it’s not a newer LED design.
To access and change the bulb in your microwave, you will need to remove the cover plate that holds the casing. It is typically held on by a screw. In some microwaves, there is no cover plate, but rather the casing just needs to be popped off with a screwdriver. Regardless of which you have, once the casing is off then you will be able to unscrew the bulb. For your specific model of microwave, you will want to consult your owner’s manual. The wattage of the replacement bulb you need will be in there as well as how to remove the bulb. If you no longer have your owner’s manual, which seems likely for most people, you can usually look it up online using your model number. That number should also help you find the right replacement bulb as well if you do not want to look through the whole manual.
If you have installed a new bulb, connected the electricity, and found that there still is no light, then we’ve got bad news. The bulb likely wasn’t burnt out, and all the other culprits will be more difficult to replace.
The Light Socket is Faulty
Moving onto the next likely culprit, you will want to investigate the light socket itself. This is where the bulb is actually put into contact with the electric current. In most cases, a contact in the socket has gone faulty which stops the required amount of electricity from getting to the bulb.
Unlike a faulty bulb, you can test a light socket with a multimeter to see if it is faulty. If there is a current of 230 volts present, than the socket is still working and you will want to investigate other issues.
Unfortunately, replacing a light socket requires disassembling the microwave more in order to disconnect the wiring and remove the socket to replace it.
Damaged Door Latch System
Your microwave has door latches that are made up of switches. One of those switches is responsible for turning on the light when the door is open or the microwave is running, and turning off the light when the microwave door is closed. If changing the bulb didn’t work and if the light socket tested just fine with the multimeter, you will want to suspect the switches. You can test each of the door switches with a multimeter to find out which is faulty and needs replacement. Keep in mind that you will need to test the switches in both the on and off position in order to get an accurate read. It is very possible that one switch is just stuck in the off position.
If all the switches technically do test as though they are working, you may want to consider the actual latch contact. If the latch is malfunctioning, then it may not touch the switch as it needs to in order to trigger it. If the latch on your microwave door is bent or broken, this is a very likely case. However, as the door latch is also safety mechanism, this becomes more suspect if your microwave sometimes does not start because it does not sense that the door is closed because the latch is faulty. If your microwave sometimes requires you to open the door and close it again in order to get it to work, the light going out is almost certainly a door switch issue.
The Circuit Board is Faulty
The final cause for this issue is that circuit board has gone faulty. As the circuit board is the brain of your microwave, it can be responsible for the light not turning on as well as a myriad of other issues. This is, with all honesty, the least likely cause of a microwave light not working, but it does have the most telling symptoms if it is the case.
As your circuit board controls everything, you will see a lot of different malfunctions if your circuit board is going faulty. This means display problems, button problems, even spotty function. The good news is that in most microwaves, the circuit board is pretty easy to replace. In most modern models, the display, control pad, and control board are all one sealed piece so you just need to take out that module and swap it out with a new one. Not a a lot of disassembly is involved as one might think.
You can technically test for a faulty circuit board with a multimeter, but again, if it is going bad, you will usually see tons of different symptoms before it goes out completely, a loss of cabinet light function among them.