The sound is normal and there’s no reason to be alarmed. If your microwave makes noises when it’s in standby that are somewhat loud or strange, something could be wrong with your fan run on. Check to see if the noise stops after a while.
Popping. You may describe the noise of your microwave as a popping noise, crackling noise, or snapping noise as you prepare foods or after spilling food. However, these tones often result from the high water content or high-fat content of foods, especially sauces.
If you hear a crackling sound during operation, you should observe the oven cavity for arcing: sparks or flashes often occurring near rack supports. Arcing can be caused by a dirty wave guide or the exposed metal of a damaged interior wall.
If your microwave is making an unusual or loud humming noise, you may have a problem with the magnetron. This component is part of the high voltage circuit and provides the microwaves that generate the heat. If the magnetron is defective, it may cause a loud humming or buzzing noise.
A thumping or rattling noise is often caused by the turntable plate not being placed in the microwave correctly or because of defective rollers. Check that the turntable plate and roller support are installed correctly.
If there’s no metal in the microwave, check the waveguide cover. That will be a small panel on the inside of the thicker side of the microwave. If it looks cracked or damaged, that’s probably the cause of the sparks. You’ll need to order a replacement waveguide, then unplug your microwave and replace it.
Boiling a cup of water in a microwave could cause it to explode. Water could be over-heated (perhaps even past boiling point), as it will just keep on heating up for a long as you’ve set it for. So when it is disturbed or moved, it’s likely that the heat will release by erupting violently.
No matter how new your microwave or if there’s only one problem, if the magnetron is out then you might as well replace the entire appliance. The magnetron is the heart of a microwave that actually makes the micro-waves. Replacing it is about equal to the cost of buying a whole new microwave, sometimes even greater.
Replacing a microwave magnetron costs $100 to $200. This includes a part price of $50 to $100 and $50 to $100 for labor. A magnetron is the primary component that produces heat for the appliance.
Although the average life of a magnetron tube is 22 years, a number of factors can cause that number to diminish and for the microwave oven to lose power more quickly.
The average microwave oven lasts about seven years with normal use, and even less with heavy use and poor maintenance. A large family may find themselves replacing their appliance every four to five years as they become more reliant on its use to heat up snacks and leftovers, or to defrost meals.