kenmore microwave not heating. went through all identified components and tests of same - diode, relay, capacitor, transformers, magnetron, switches, fuses, sensors/thermostats.

diode - 9v battery check with DMM, checks okay not open or shorted. capacitor - resister check okay, uF checks 1.03 for 1.05uF rated. no defect - but curious no spark or pop when attempt to discharge after each test. Transformer- resisitance checks okay on primary, secondary, and to ground. magnetron - terminals and to ground resistance checks okay, nose of antenna okay, visual no defects of burns. relay - 120 v to transformer and checked on various power scales 1-10.

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    I'm voting to close this question as off-topic because I don't think we can deal with a mystery microwave failure out here. – ThreePhaseEel Jan 5 '16 at 5:07
  • This should NOT be closed and is VERY useful! @Ojait DID answer his question, and did so quite well. I would bet that the magnetron IS bad, as described below. I repaired TWO KitchenAids for less than $80 TOTAL, and on both, the magnetron could NEVER be determined as bad, using normal tools. (Add MY repair guide I just wrote, to his excellent answer). – DaaBoss Dec 21 '18 at 18:27

I've found from repairing and "hacking" microwaves that they all follow a flow chart when a symptom prevents it from working normally.

From what I can recall about the symptom "unit not heating" and if that is the only symptom, the primary parts that are suspect are (in order of most likely the problem): 1). the High Voltage Diode (HVD). It should show continuity in one direction only. These are subject to large jolts of energy and if they are low quality will fail. Not very expensive to purchase and quickly replaced. 2). the Magnetron has parts that if jolted or jarred will break easily. It is difficult to test with anything but special tools made for the magnetron. Check for the correct voltage at its' terminals and if all other components are working replace it. 3).the Capacitor will go south eventually no matter what quality. Visually check for bulging in the wall and replace if found. After discharging, check with a DVM by setting the dial to ohms. When the probes touch each terminal the reading should be rising. Alternate the probes and the reading should go down. Replace if it shows continuous continuity.

With todays low priced microwaves, unless you are repairing them to learn or as recreation (or your being paid), replace the non-working unit with a new one.

On a side note, I've learned a lot about repairing microwaves with this book by Homer L. Davidson, "Troubleshooting and Repairing Microwaves".


Get a new microwave or check absolutely everything. It may just be the door switch, but it could even be the turntable motor. If it's lacking proper operation most anywhere it would die. The only microwaves that last for me are Panasonics, virtually flawless for 20-years on 1 & totally flawless for 10-years now on another & bought the 2nd one again 5-years ago for my parents & it's flawless so far too.

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