Microwave is working perfectly, but it doesn't warm up. Ghasem
Answer Ghasem, No the the inline 20 amp fuse would not be he problem, or the thermal fuses, the microwave would be "dead" if that were the case. Your most likely culprit is a bad control board WB27X10874 or magnatron WB27X10880, if you are not familliar with high voltage, capacitors,transformers,etc. you need to be very carefull, so you don't hurt yourself. Thanks, and Good Luck
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Microwave will not heat up.
Answer Hello Donna. You most likely have a "high voltage" side malfunction. Transformer, diode, magnetron, Capacitor. You will need to be extremely careful if you decide to test the components with a multi meter, Very high residual voltage is present, so make sure you remove power to the microwave and short across the terminals on the capacitor. The magnetron should have a reading of less than 1 ohm resistance across the two terminals, and an "open" circuit between each terminal and chassis ground. The diode/rectifier should have a resistance reading in one direction only, no resistance, or resistance in both directions indicate a faulty diode. The primary winding on the trans former should read approximately 450 Ohms resistance, the secondary winding should read 80 ohms resistance, and the filament transformer should read 100 ohms resistance. If all the readings are proper and in range, replace the magnetron.