Microwave runs but doesn't heat
When the light comes on, the turntable turns and the fan runs, but the food stays cold, the control side is working and the high-voltage side is not.
Not urgent A microwave that runs without heating is not dangerous to leave alone, but it is dangerous to open: the high-voltage capacitor inside can hold a lethal charge after the plug is pulled.
What this symptom usually means
When the light comes on, the turntable turns and the fan runs, but the food stays cold, the control side is working and the high-voltage side is not. Before assuming a failure, rule out the settings: a timer running instead of a cook cycle (GE lists this first), a power level set to 10 percent, a delay start, or a demo mode that runs everything except the heat. A door that has not latched fully will also stop the heat while the light stays on, and a worn door switch can do the same.
Beyond that, the possibilities are inside the sealed cabinet: the magnetron, the high-voltage diode, the capacitor, the high-voltage transformer, or a door interlock switch. GE's support page says plainly that it offers no do-it-yourself advice for microwaves because the capacitor can retain a dangerous charge after unplugging. We say the same. Whether that repair is worth doing depends almost entirely on what kind of microwave it is, which is covered below.
Checks you can do yourself
- SettingsCancel everything, then set a fresh cook cycle at full power for one minute with a cup of water inside. Check that Timer, Delay Start, Demo or a low power level was not selected. Look for a lock or L code on the display.
- DoorOpen the door and close it firmly until it clicks. If the door does not close squarely or feels loose, stop; a door that cannot latch is a reason to book, not to keep trying.
- ResetUnplug the microwave (or switch the breaker off for a built-in) for one minute and try again. Nothing more than that.
- PowerIf it is a countertop unit, plug a lamp into the outlet. Do not run a microwave on an extension cord or a shared power bar.
- Water testHeat 250 mL of water for one minute on full power. If it comes out hot, the microwave is heating and the earlier problem may have been settings or a food-load issue. If it is cold, the high-voltage side is not working.
Nothing above involves gas, wiring, refrigerant or removing panels.
What our technician checks
These need panels off, live electrical tests or a licensed trade, so they are left to the technician:
- Removing the cabinet cover for any reason
- Discharging or testing the capacitor, diode, transformer or magnetron
- Adjusting or replacing the door, hinges, interlocks or waveguide cover if it involves opening the cabinet
Gas appliances, commercial equipment, and Thermador, Miele, Viking, Wolf and Fisher & Paykel appliances: $129 + tax.
Waived when you proceed with the repair. You get the cause, the price and our repair-or-replace verdict in writing before any work.
Repairs a technician may recommend
After inspection, not from the symptom alone.
Door switch or interlock replacement
When the door does not register as closed. A modest repair that is usually worth it on any built-in or over-the-range unit.
Magnetron replacement
When the magnetron has failed. Often worth it on a built-in, drawer or over-the-range unit; rarely worth it on a basic countertop model.
High-voltage diode, capacitor or transformer replacement
When one of those has failed; the technician discharges the capacitor before any test.
Control board or relay replacement
When the control never energises the high-voltage circuit.
Replacement recommendation
On a countertop microwave of ordinary value, the finding will usually say the repair does not make sense against a new unit, and we say so before the visit if you tell us the model.
Brands we see with this problem
Codes, parts and access differ by brand; the brand pages cover where the model label is and what to expect.
Cost, and whether to fix it
What the repair costs depends on the part, the labour and whether a second visit is needed for an ordered part; the written finding gives the total before any work. Our guides on what drives repair costs and repair versus replacement explain how to weigh it.
Who to call
RepairWell diagnoses and repairs this in homes and businesses across Ottawa and Gatineau; the diagnostic ($89 + tax at home, $129 + tax for a business) is waived when you proceed with the repair. If the microwave is still under the manufacturer's warranty, contact the manufacturer first: warranty repairs usually have to go through their authorized network.
When to book
Be honest with yourself about the unit first. A built-in, drawer or over-the-range microwave is installed into cabinetry, is often part of a matched suite, and costs enough that a magnetron or door-switch repair is frequently the sensible choice; book those. A basic countertop microwave often costs less to replace than a diagnostic plus parts, and we will tell you that up front rather than send a technician. If you send us the model number, we will say which side of that line it falls on. When a visit does make sense, the diagnostic is $89 + tax, waived if you proceed, and the finding gives the repair figure against a replacement. See microwave repair.
We handle this across Ottawa and Gatineau
Related problems
Microwave runs but doesn't heat: questions
Is it really unsafe to open a microwave?
Yes. The high-voltage capacitor can hold a charge well after the unit is unplugged, and the magnetron and transformer operate at voltages far above anything else in the kitchen. Manufacturers give no home repair advice for the interior, and neither do we.
Is my countertop microwave worth repairing?
Usually not, unless it is a high-end or commercial unit. A visit plus a magnetron will often exceed the cost of a comparable new microwave. Tell us the model and we will say before you book.
My over-the-range microwave stopped heating but the fan and light work. Is that repairable?
Often, yes. The fan and light are on the low-voltage side; a failed door switch, diode or magnetron is a repair we do on built-in and over-the-range units, and the finding shows the number against replacement.
The microwave sparks when I use it. Is that the same problem?
No. Arcing usually means metal in the cavity, a damaged waveguide cover, or chipped interior paint. Stop using it and book; continued arcing can damage the magnetron.
Sources
- GE Appliances: Microwave runs but does not heat
- Whirlpool: Microwave not heating, possible causes and fixes
Sources checked 2026-09-24.
Book the diagnostic
Tell us this symptom and your postal code; it helps us bring the right parts.
Pick a preferred day and arrival window online; we confirm by email once a technician is assigned.
- $89 + tax diagnostic$129 + tax for gas or commercial appliances and for Thermador, Miele, Viking, Wolf or Fisher & Paykel; waived when you proceed with the repair
- Written finding on every visitCause, price and our repair-or-replace verdict
- 90-day warrantyOn parts replaced; labour depends on the work done