Most microwave problems come down to one of three things: a heating circuit fault (door switch, diode, or a setting like Demo Mode), sparking caused by metal or a dirty waveguide cover, or a turntable that’s stopped turning because of grease buildup. This guide sorts common failures by symptom, so you can jump straight to the section that matches what your microwave is actually doing.
Every symptom page below ranks causes by how often they turn out to be the real problem, includes at least one check you can run without buying anything, and tells you plainly when a fix is a quick job versus when it’s time to call a professional. Microwaves carry a real electrical hazard that most kitchen appliances don’t: the high-voltage capacitor can hold a lethal charge even after the unit is unplugged, so we’re explicit about which repairs are DIY-safe and which aren’t.
Microwave Not Heating
If the light, turntable, and fan still run but food stays cold, rule out a tripped breaker and Demo Mode before suspecting a hardware fault. See Microwave Not Heating: 7 Causes Ranked by Likelihood for the full diagnostic order.
Microwave Sparking or Arcing
Sparks almost always trace back to metal left in the cavity or a grease-soaked waveguide cover, both fixable in minutes and both reasons to stop using the microwave until resolved. See Microwave Sparking or Arcing Inside? Causes and When to Stop Using It for the full breakdown.
Microwave Turntable Not Turning
Grease and food debris on the roller guide cause most stuck turntables, well ahead of a worn drive coupler or motor. See Microwave Turntable Not Turning? 3 Causes Ranked by Likelihood for the full diagnostic order.
Microwave Tripping Breaker or Blowing Fuse
A breaker that trips only once the microwave starts running points to an internal short, most often the door switch before the capacitor, magnetron, or transformer. See Microwave Tripping Breaker or Blowing Fuse? 5 Causes Ranked by Likelihood for the full diagnostic order.
Microwave Door Won’t Close or Open
Food debris or grease around the latch causes most cases, well ahead of a worn latch hook or a faulty door switch. See Microwave Door Won’t Close or Open? 5 Causes Ranked by Likelihood for the full breakdown.
Microwave Won’t Turn On
A dead outlet or tripped GFCI causes more no-power microwaves than any internal fault. See Microwave Won’t Turn On? 5 Causes Ranked by Likelihood for the full diagnostic order.
Microwave Buttons or Keypad Not Working
Control Lock and grease buildup cause most unresponsive keypads, well ahead of a worn touchpad or a failed control board. See Microwave Buttons or Keypad Not Working? 5 Causes Ranked by Likelihood for the full breakdown.
Preventive Maintenance
Wipe up food splatter after every use, especially on the waveguide cover, since carbonized grease there is the leading cause of interior arcing. Wash the glass tray and roller guide every week or two so debris doesn’t build up enough to stop the turntable from turning. Never run the microwave empty or with the waveguide cover removed, and always use microwave-safe containers free of metallic trim or twist ties. If you smell burning or see any discoloration inside the cavity, stop using the microwave until you’ve identified the cause.
Repair or Replace?
Cleaning fixes and cheap parts like the waveguide cover, drive coupler, and turntable motor all stay well under $30, so repairing wins easily when one of those is the cause. Diode, capacitor, and magnetron failures are pricier and involve a genuine electrical hazard, so professional labor adds to the cost; once a quote approaches half the price of a new microwave, especially on a unit already several years old, replacing is usually the better call. For the full cost breakdown, see our microwave repair cost guide.
When to Call a Professional
Call a technician for anything involving the diode, high-voltage capacitor, or magnetron: these parts sit behind the cabinet and the capacitor can hold a lethal charge even after the microwave is unplugged. The same goes for any chipped interior enamel exposing bare metal, a burning smell, or scorch marks. None of the diagnostics on this site are a substitute for a professional opinion when something feels genuinely wrong.
Frequently Asked Questions
Can I repair the appliance myself?
Simple checks (filters, seals, settings) are accessible to anyone, appliance unplugged. Electrical work should be left to a professional.
Are the suggested diagnoses guaranteed?
No. These are leads based on the most frequent causes, never certainties.
What if my error code isn’t listed here?
Check your model’s manual: the same code can vary by brand and year.
The information provided here is a diagnostic aid and does not replace the intervention of a qualified professional.