Demo mode can run the display and fan without producing microwave energy. A kitchen timer or reduced power setting creates another cold result without a failed magnetron.
The cabinet stays closed even after the plug is removed. CPSC warns that stored high voltage inside a microwave can cause fatal shock.
Before you touch it
Checks that can change the diagnosis
- Confirm Demo mode is off.
- Use a normal cook cycle at full power.
- Clean the door contact area.
- Check the door closes firmly.
- Confirm the required ventilation clearance.
Try this in order
The safe troubleshooting sequence
Exit Demo mode
Use the model menu rather than guessing a key combination.
Select a real cook cycle
Choose full power rather than Kitchen Timer, Warm or a reduced power level.
Clean the door area
Unplug the microwave and wipe the door and frame with a damp cloth, then dry them.
Check clearance
For a countertop model, confirm that the vents have the space required by the manual.
Run one water test
Place one cup of water in a microwave-safe cup and heat for one minute at full power. Use an oven mitt.
Stop after one cold result
Unplug the appliance and arrange service. Do not remove the cabinet to inspect a fuse, magnetron or capacitor.
How you know the simple fix worked
The test water should become clearly warmer. A cold cup after correct settings and door closure confirms that the safe external checks are finished.
Technician territory
Stop the job when you see any of these
- Cold water after one correct test
- Burning smell, sparks or an abnormal loud hum
- A damaged door or operation with the door open
- Any cabinet removal
The claim can change the repair decision
Maintenance, a warrantyWritten warrantyA written promise supplied with the appliance sale. Federal law treats it as part of the product bargain rather than a separate paid plan. and a service contractService contractA separately purchased agreement that pays for stated maintenance or repair during a fixed period. Sales pages often call it an extended warranty. are different things.
A magnetron or high-voltage repair may approach replacement cost on a countertop unit. Check any magnetron warranty and plan limit before authorizing work. Federal warranty protections do not make every DIY mistake covered, and a paid service contract may require authorization before a part is replaced.
Common questions
The short answers
Can an unplugged microwave still shock me?
Yes. CPSC warns that internal high-voltage parts can retain a dangerous charge. Never open the cabinet.
Should I test an empty microwave?
No. Use the model's supported water test and never operate it empty.
Instructions checked against primary sources
Official guidance used for this fix
- SamsungMicrowave runs but does not heat
- CPSCMicrowave DIY electrocution warning
- Federal Trade CommissionWarranty restrictions and damage caused by independent repair
Guide reviewed August 2026. Model construction varies. The owner manual and recall notices for the exact model take priority over a general guide.