Quick answer
A microwave that runs, lights up and turns the plate but does not heat food usually has a failed high voltage part: the diode, capacitor, transformer or magnetron. These parts store dangerous voltage even when unplugged, so do not open the case. Appliance Repair Philly repairs microwaves across Philadelphia, and the diagnostic is $60 flat, credited toward the repair.
Safety first
The high voltage capacitor in a microwave can hold a lethal charge after the plug is pulled. Never remove the outer cover or touch the inside. This is a job for a trained technician. If you smell burning, see sparks or hear loud buzzing, unplug the microwave and stop using it.
Check these first
- Try a different outlet. Plug the microwave straight into the wall, not a power strip.
- Check the breaker. Built-in and over-range units can share a circuit.
- Test with a cup of water. Heat one cup for one minute. If it is still cold, the heating system is out.
- Turn off demo or lock mode. Some models have a lock or showroom mode. Check the manual.
- Look at the door. A bent door or a damaged latch can stop the heating circuit from starting.
Likely causes
| Part | What to notice | Repair or replace |
|---|---|---|
| High voltage diode | Runs normally, no heat | Often repair |
| High voltage capacitor | Runs, no heat, sometimes a hum | Often repair |
| Magnetron | Loud buzzing, burnt smell, no heat | Depends on age and price |
| Transformer | Humming, no heat, a blown fuse | Usually only on older units |
| Door switches | Dead or unstable, fan runs but no start | Often repair |
| Thermal fuse | The microwave is dead, not just not heating | Repair, find the cause |
| Control board | Display problems, random shutoffs | Depends on model |
Built-in, over-range or countertop
Over-range microwaves are costly to remove and replace because of the mount, venting and cabinet fit, so repair is more often worth it, especially on a unit under 8 years old.
Built-in microwaves are trim-kit units that fit a cabinet cutout. A replacement with the same size is sometimes hard to find, so repair is attractive.
Countertop microwaves are cheap. A $60 diagnostic plus a repair of $150 or more can be close to the price of a new one. For basic countertop units we say honestly when replacement makes more sense.
What the technician does
The technician checks the door switches and fuse, tests the diode, capacitor and magnetron with the right meter and discharge tools, and checks the control. Then we explain the price. If the repair costs more than half of a comparable new microwave, we say so.
What it costs
| Fault | Typical total with part |
|---|---|
| Diagnostic | $60 flat, credited to the repair |
| Door switch or latch | $120 to $220 |
| Diode or capacitor | $150 to $260 |
| Magnetron | $200 to $350 |
| Control board | $200 to $400 |
| Turntable motor, light, fan | $100 to $220 |
Repair or replace
Microwaves last about 9 years on average. Use the 50 percent rule. If the quote is more than half the price of a new similar microwave, replace a countertop unit. For over-range and built-in models, repair if the unit is under 8 years old. See the cost guide.
How it works
- Call or send the brand, model and what you see.
- Call to check the next open appointment; availability depends on the schedule.
- Diagnosis and a clear price. The $60 is credited if you go ahead.
- Repair and test. Ask what the repair includes when you book.
More on the whole appliance: microwave repair. We come to Philadelphia, Northeast Philadelphia, Bensalem, Willow Grove, Abington, Huntingdon Valley, Southampton and Feasterville-Trevose.
FAQ
Why does my microwave run but not heat?
Usually a failed diode, capacitor or magnetron in the high voltage circuit.
Is it safe to fix a microwave myself?
No. The capacitor stays charged after unplugging and can be lethal.
How much does it cost to fix a microwave that won’t heat?
Most repairs are $150 to $350. The $60 diagnostic is credited toward the repair.
Is it worth repairing a microwave?
For over-range and built-in units, often yes. For a cheap countertop one, compare with a new one.
Is it safe to use a microwave that sparks?
No. Stop using it. Sparks point to a damaged cavity cover, a metal item or a failing part.