Over-the-range and built-in microwaves
Microwave repair
Countertop microwaves are rarely worth repairing. Over-the-range, drawer and built-in units are tied into the cabinets and venting, so a repair often makes sense. Microwaves store a dangerous charge in the capacitor even when unplugged, so internal repairs are not a DIY job.
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Repair or replace?
- Act now
Smoke, burning smell or arcing that continues with no metal inside
Stop and unplug it.
- This week
Over-the-range or built-in unit with a fuse, switch or diode fault
Usually worth repairing.
- Plan it
Countertop unit needing a magnetron or board
Replacement is usually the better choice.
Microwave parts that fail most
- Door interlock switches
- Wear with every opening and are a common cause of a dead unit.
- High-voltage diode
- A small, common failure that stops heating.
- Magnetron
- The heat source. A larger repair, and the main point to weigh against replacement.
Microwave symptoms and causes
| What you notice | Usual cause | Usual fix |
|---|---|---|
| Runs, turntable turns, food stays cold | Failed magnetron, diode or capacitor | Component tested and replaced |
| Completely dead | Blown main fuse, often from a failed door switch | Fuse and door switches replaced |
| Sparking inside | Metal in the dish, or a damaged waveguide cover | Remove metal; cover replaced |
| Keypad does not respond | Worn membrane or control board | Keypad or board replaced |
| Vent fan noisy or not running | Fan motor or switch | Motor replaced |
How the repair is done
Discharge safely
The technician discharges the capacitor before touching anything inside.
Test the circuit
Fuse, switches, diode, capacitor and magnetron are tested in turn.
Leakage check
After the repair, the door seal and cavity can be checked with a microwave leakage meter.
Safe checks only
Do not remove the outer cover. The capacitor can hold a lethal charge after unplugging.
Check the outlet or breaker
Over-the-range units are usually plugged into an outlet in the cabinet above.
Test with water
Heat a cup of water for one minute. If it barely warms, the heating circuit has failed.
Inspect the waveguide cover
A small panel inside the cavity. Burned spots on it cause sparking and can be replaced.
What can be repaired on a microwave
Microwave energy comes from a magnetron fed by a high-voltage transformer, capacitor and diode. Door switches stop it when the door opens. Over-the-range models also have a vent fan and cooktop lights, which fail on their own.
- Heating circuit
- Magnetron, high-voltage diode, capacitor and transformer.
- Door safety
- Interlock switches and the door latch. A failed switch often blows the main fuse.
- Vent and light
- On over-the-range units, the exhaust fan motor, damper and cooktop lights.
- Controls
- Keypad membrane and control board.
What changes a microwave job
- Mounting
- Over-the-range units often have to come down from the wall bracket for internal repairs, which takes two people.
- Venting
- Units vented outside need the damper and duct reconnected when reinstalled.
- Parts
- Magnetrons and boards are the largest parts to replace.
Microwave Repair: common questions
Why is microwave repair dangerous?
The high-voltage capacitor can hold a charge long after the microwave is unplugged. Internal repairs should be done by someone trained to discharge it.
Can I install an over-the-range microwave myself?
It needs a solid wall bracket fixed to studs, a top cabinet template and an outlet in the cabinet above. Two people are needed to lift it. See appliance installation.
Why does my microwave turn on by itself?
A stuck keypad or a failing control board. Unplug it until it is checked.
Talk to a technician about microwave repair
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