Microwave not heating?

The microwave runs, the light and turntable work, but the food stays cold. The cheap causes are on the outside: a door that isn't latching, a power level set too low, or a lock mode. If those check out, the fault is behind the case (a fuse, diode or magnetron) and that is for a pro.

Not sure which one it is? Snap your microwave and we’ll narrow it down.

Does it spark or arc inside instead?

Sparking has its own causes, and it should be stopped right away. Microwave sparking

Likely causes

Door not latching, or a failed door switch
Most commonCall a pro
The door doesn't click shut, hangs loose or is bent, or the microwave won't start at all, or starts and runs without heating. The switches are small levers behind the latch hooks.
Part: $50–100 for a pro repair
Wrong power level, or a demo or child lock
Most commonEasy DIY
The display shows a low power level (such as 10%), a lock icon, or demo mode, and the unit counts down with the light and fan on but doesn't heat.
Blown fuse
CommonCall a pro
The microwave is completely dead: no display, no light, no fan. This can follow a power surge. The fuse is inside the case, so this is a pro repair.
Part: $75–200 for a pro repair
Failed high-voltage diode
CommonCall a pro
Everything runs normally, the turntable turns and the light is on, but the food doesn't heat. Sometimes there is a humming or buzzing sound.
Part: $55–130 for a pro repair
Failed magnetron
Less commonCall a pro
No heat, often with a loud hum, buzz or burning smell when it runs. The magnetron is the part that makes the microwaves.
Part: $100–200 for a pro repair
Failed control board
Less commonCall a pro
The display is blank or scrambled, buttons don't respond, or the unit starts and stops by itself while the door and power check out.
Part: $100–300 for a pro repair

Quick checks

Never open the outer cabinet. The high-voltage capacitor inside can hold a dangerous charge even when the microwave is unplugged, so anything behind the outer case (fuse, diode, magnetron, capacitor) is for a pro. Don't use a microwave whose door is damaged or won't close properly. If you see smoke or a flame inside, keep the door shut and unplug it. If the fire doesn't go out within a few seconds, leave and call 911. Over-the-range units are heavy and need two people to remove.

Close the door firmly and watch whether it clicks shut. Look for a bent door, a broken hook or food stuck in the latch.
Check the display for a low power level, a lock icon or a demo mode, and reset the power level to high.
Try a cup of water for one minute. If the water stays cold but the light and turntable work, stop and plan on a pro or a replacement.
Make sure the plug is fully seated, and try a different outlet to rule out a tripped GFCI or a dead outlet.
Write down the model number from the label, and any error code on the display.

Sharpen the read

Diagnose your microwave in seconds, for free

No account, no phone number. Fixology’s AI reads your photo and tells you what’s likely wrong, how worried to be, and whether it’s a DIY fix.

Snap one of these:

the door latch and hinges
the display and any error code or lock icon
the model label (inside the door frame or on the back)

Add a note or more photos next. Nobody calls you.

When to call a pro

Anything behind the outer case: a dead microwave with a good outlet, a hum or burning smell with no heat, a blank or scrambled display, or a door that won't latch. A budget countertop microwave over 10 years old is often cheaper to replace than repair. For lifespan and upkeep, see the microwave guide. If it sparks, see microwave sparking.

Typical cost: $100–200 for a typical microwave repair (about $175), up to about $500 for door replacements and built-in or over-the-range units. Expect a $50–100 service call plus $50–150 an hour in labor. Countertop repairs run $50–350 and over-the-range or built-in repairs $50–500.

Sources: HomeAdvisor: How much do microwave repairs cost? (updated June 19, 2026)

After a scan, Fixology can also help you find pros near you.