5 Reasons Why LG Microwave Not Heating – Let’s Fix It

If you’re having trouble with your LG microwave not heating, there are a few troubleshooting steps you can try. If your microwave is just not heating food, the first thing to do is check the power source by plugging the device into another outlet. If the microwave works, it could be that outlet was faulty. If it doesn’t work, it could be that the microwave itself is broken.

Your LG microwave isn’t heating up, and you might be wondering why. It could be due to one of several common problems. The microwave’s magnetron or capacitor may be defective, the fuse may have blown, or there may be an issue with one of the other components.

LG Microwave Not Heating – Troubleshoot and Diagnosis

IMPORTANT: Microwave ovens can be dangerous machines when in the wrong hands – they contain lethal amounts of electricity. Never, under any circumstances, should you try to fix something in your microwave or attempt to make any adjustments to it. Instead, seek the help of professionals who are well-versed in working with microwaves.

LG Microwave Not Heating

When your microwave experiences issues, you should troubleshoot to see if it’s something you can fix yourself before you call an appliance repairman. I recommend checking the following things before you call:

  • Ensure that Timer function is not ON
    Sometimes, you may accidentally hit the timer button on your microwave instead of the cook button. The timer is strictly a feature that acts as a way of counting down the time, not a way of cooking your food. The problem with this? Your food gets cold and you have to heat it up again.
  • Ensure that door is properly closed
    The microwave door must be closed for the microwave to run. If the door is not completely closed, it may not heat food correctly or at all. You may even damage your microwave by slamming the door open or closed.

Your LG microwave is not heating up. There are several reasons why.

Faulty Diode

Microwave ovens use high-voltage electricity to heat food quickly. The microwave diode is a semiconductor that rectifies the A/C power from the transformer into D/C electricity, which powers the magnetron. The magnetron then produces microwaves that penetrate the food and cause it to heat up.

If the microwave diode burns out, it won’t get enough voltage to operate. That means your magnetron won’t be able to produce any waves – and your product will stay cold.

When the microwave stops heating food, the diode might be burned out. Inspect the diode and replace it if it’s burned out.

Defective Door Switch

As much as microwaves are simple, they are equipped with an array of door switches that can all fail given enough time. There are many issues that can arise from the breakage of these switches, but the most common issues could be that your microwave will not heat or stop working.

Test all of the microwave door switches to make sure they have continuity. If any don’t, replace it.

Burnt Out Magnetron

If your microwave doesn’t heat food up, it’s because the magnetron has failed. A magnetron is a component in a microwave that generates microwave radiation using high-voltage, direct-current electricity and works along with a waveguide to produce microwaves within the oven. When a magnetron fails and the microwave doesn’t heat, it must be replaced in order for the microwave to work again.

Burnt Out High Voltage Capacitor

The High Voltage Capacitor is an often overlooked component in microwaves. Its job is to regulate the voltage. This means that it takes the AC voltage from the transformer, and turns it into DC voltage for the magnetron. If your capacitor is burnt out, you can either replace it or repair it by adding a couple diodes. If you are not feeling confident about this repair, call a professional instead of attempting to diagnose and fix it yourself.

If you’re having trouble with your microwave, you will need to check the capacitor first. Using a digital multi-meter (DMM), check your capacitor and ensure it has a capacitance reading of between 5 and 60 microfarads — any less or more and we’ll need to replace it.

Failed High Voltage Transformer

When a transformer is broken, you might notice that you’ll be getting an electric shock from your microwave. In addition to leaving a burning smell, microwave transformers can potentially cause fires.

Blown Thermal Fuse

The thermal fuse is an internal protection device which cuts off power to the microwave if the microwave overheated. The fuse will automatically reset and allow the microwave to resume working when it cools down — but don’t run the risk of causing permanent damage.

If your microwave is not heating, there may be a problem with the thermal fuse inside. To test if it has blown, use a multimeter to check for continuity. If you get no reading on the multimeter, replace the fuse.

Tripped Thermoprotector

The thermoprotector is a safety mechanism that shuts down the microwave if it gets too hot. If tripped, your device may have overheated — and you can check under the protective cover to see if any of the wires are loose. These issues typically stem from a lack of ventilation, such as keeping the microwave close to other appliances or failing to leave enough space around it for air to circulate.

Defective Main Control Board

Although it is rare, some customers have reported that their microwave stopped heating properly after prolonged heavy use. If this is the case, your LG microwave’s main control board may have failed due to overheating or damage. We recommend contacting LG about a replacement main control board.

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