The short answer
A countertop microwave that runs without heating usually comes down to one thing: the membrane keypad is registering the wrong setting. Next on the list: the power level or the programme is set low. Before anything else, heat a measured cup of water at full power for a timed minute — that single test tells you whether the oven has a real fault or a setting.
What you observe
- The oven runs normally and the food stays cold — Light on, fan running, plate turning, and nothing gets warm.
- The display does not always match what you pressed — The fault is between the keypad and the control.
- Food warms, just far more slowly than it used to — Slow is a power level; stone cold is not.
- Part of the food is scalding and part is cold — Standing waves make hot and cold spots when nothing moves.
- NEAR MISS — food heats unevenly rather than not at all — That is usually the turntable or the load, and it reads differently from no heat.
Causes, most likely first on this machine
- The membrane keypad is registering the wrong setting — First on this oven, because its controls are a printed membrane behind a flat panel, and those wear from the back.
- The power level or the programme is set low — Ranked here because it costs nothing to check and it explains an oven that is slow rather than cold.
- The turntable is not turning — Ranked here because the symptom is uneven heating rather than no heating, and that distinction is the whole diagnosis.
- The load is too large or too dense for the oven — Last, and separated by the water test: a cup of water heats or it does not.
Check in this order, and why
- Watch the display carefully as you press each key — A worn membrane registers a neighbour, not the key you pressed.
- Set full power and heat a cup of water for a timed minute — A reduced power level looks and sounds exactly like full power.
- Watch through the door and check the plate is rotating — Uneven heating and no heating are different faults.
- Heat a cup of water and compare it against the real load — The water test tells you what the oven can do, load aside.
What an owner can safely check
- Heat a measured cup of water at full power for one timed minute — Clearly hot means the oven works. Stone cold is a real finding.
Tools: measuring cupAbout 10 min
- Press each key in turn and check the display agrees — Note which keys misbehave; it is a useful report.
About 15 min
- Set full power and time one minute on a cup of water — Warm water means the oven works and the setting was the fault.
Tools: measuring cupAbout 10 min
- STOP HERE — nothing beyond this point is owner work on a microwave — The case stays on. A capacitor inside holds a dangerous charge after unplugging.
Before you open anything
Safety
Unplug the appliance before removing any panel — and on a microwave, do not remove one. A capacitor can hold a charge after the power is off, and in this appliance that charge is dangerous. On this appliance the rule is absolute: the case does not come off. A microwave contains a high-voltage capacitor that can hold a dangerous charge long after it is unplugged, and no symptom on this page justifies opening it. Never run the oven empty, never bypass a door interlock, and never use it with a damaged door or screen.
When to call a technician
Call once the setting, the turntable, the load and the ventilation are all ruled out and a measured cup of water is still cold after a timed minute. On a compact oven, ask about the cost of the repair against a replacement before agreeing to it. Call immediately — and unplug the oven first — if you smell burning, see a flash inside, or the oven trips its breaker when heating starts.
Nearest pages of this class
What this page does not cover
This page is written for the brand and the appliance class, not for one family or model line. Where a family- or model-specific page exists for your oven, that page is the more specific answer.
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
