How to Test a Microwave Oven to See if it’s Heating Properly

Suspecting your microwave oven of slacking off on the job? Here’s a quick and easy test that’ll let you check your microwave oven’s heating output without needing to buy fancy equipment; only things you’ll need are a 1 liter PYREX glass bowl and a thermometer that can measure the temperature of hot water.

IMPORTANT: Make sure the bowl you are using is PYREX glass or another brand of glass that explicitly states it is microwave safe. DO NOT use plastic (inaccurate) or metal (DUH!).


1. Fill the PYREX bowl with water at room temperature. Record initial water temperature.

2. Run the microwave on high power for 2:03. Not 2:04, nor 2:02 except ye go on to 2:03. 2:05 is right out.

3. Record end water temperature.

If the microwave magnetron is working right, the minimum difference between the initial and ending temperature should be about 86℉. If it’s much less than this, then you probably have a weak magnetron. If water temperature hardly changes at all, then there’s something wrong with the high voltage section and you’ll need to troubleshoot it. Suspects include: magnetron, HV transformer, HV capacitor, HV rectifier, and door interlock switch among others.

To learn more about your microwave oven, or to order parts, click here.


One thought on “How to Test a Microwave Oven to See if it’s Heating Properly

  1. qwiksilver96

    Your recommended test procedure is flawed. It is important to measure the quantity of water to be heated. One would receive varied results were they to heat 10 oz of water vs 30 oz of water.

    FYI, a delta of 86 deg Fahrenheit would indicate a microwave oven outputting 1668 watts of cooking power for 1 liter of water.


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