Microwave not heating and making loud noise
Prices checked 2026-08-28
A microwave not heating is most often a failed door interlock switch problem - about 34% of reported jobs. Here is how to confirm it, what the part costs, and when to stop.
A microwave is a magnetron, a high-voltage circuit and a door interlock – the last one being the part that protects you. Most faults are either the door switch or the high-voltage side.
Microwave not heating and making loud noise is one of the most common repair searches there is. When a unit that should produce heat stops doing it, the first instinct is to call someone – but most no-heat faults are one of a handful of parts, and a few of them you can confirm yourself in minutes. The list below is ranked by how often each cause is the real one, with the part name and what the fix typically runs.
Before you call anyone: 30-second checks
- Check the breaker or fuse first – a tripped breaker is the cheapest "repair" there is.
- Confirm the unit is actually getting power and the controls are in the right mode (heat, not fan-only).
- If it runs but produces no heat, listen for the igniter or element click; silence points to the ignition or element circuit.
- Look for a reset button or high-limit switch – they exist exactly for this failure and trip far more often than owners expect.
The likely causes, ranked
Failed door interlock switch
About 34% of microwave not heating and making loud noise jobs come back to this cause. Switches and interlocks tell the unit it is safe to run, and a stuck or failed switch can stop a unit dead or leave it running when it should not.
How to confirm it: A unit that will not start, or starts only when the door is held, points at the interlock switch – a cheap, common part.
Typical fix: $50. A capable DIYer can usually handle this one. You would be looking for a interlock switch.
Failed magnetron
About 30% of microwave not heating and making loud noise jobs come back to this cause. This is a component-level failure – the part itself has worn out or failed, which is why it sits on the ranked list rather than the free-check list.
How to confirm it: It is worth confirming with a multimeter or a visual check before ordering the part, and worth asking the shop if the part is returnable.
Typical fix: $150. This one is best left to a professional. You would be looking for a magnetron.
Failed high-voltage diode or capacitor
About 22% of microwave not heating and making loud noise jobs come back to this cause. A motor, fan or pump with its drive components is a wear item – belts stretch, bearings dry out, capacitors lose their charge and relays stick.
How to confirm it: Listen for the motor: a hum with no movement points at a capacitor or belt; a grinding or squeal points at a bearing. Each has a different price tag.
Typical fix: $60. This one is best left to a professional. You would be looking for a high-voltage diode.
Bad control board or touchpad
About 14% of microwave not heating and making loud noise jobs come back to this cause. The control board, timer or sensor is the brain of the unit, and it fails by misbehaving rather than dying – wrong readings, stuck relays, forgotten cycles.
How to confirm it: Look for error codes, behaviour that changes with settings, and any burnt smell near the board; boards are the last part to blame and the last to buy.
Typical fix: $160. This one is best left to a professional. You would be looking for a control board.
When to stop and call a pro
If you smell gas, see flames that look wrong, or the unit has not been serviced in years, stop and call a licensed trade. Heating circuits are one place a wrong guess gets expensive fast.
How to keep it from coming back
Most no-heat callouts come back to airflow and maintenance that was deferred. Keep filters, vents and burner areas clear, and have gas-fired units serviced on schedule so the ignition and safety circuits are checked before they fail.
Bottom line: Microwave not heating and making loud noise is worth diagnosing before you call anyone – the free checks above catch a surprising share of cases, and the ranked list tells you what the part should cost if it is not one of them. Run the figures through the repair-or-replace test on this page before you authorise any work, and never pay for a diagnosis without getting the part name and the price in writing first.
Likely causes, most common first
| Likely cause | How often | Typical fix | Who does it |
|---|---|---|---|
| Failed door interlock switchinterlock switch | 34% | $50 | DIY-able |
| Failed magnetronmagnetron | 30% | $150 | Pro job |
| Failed high-voltage diode or capacitorhigh-voltage diode | 22% | $60 | Pro job |
| Bad control board or touchpadcontrol board | 14% | $160 | Pro job |
Frequencies are the share of reported jobs attributed to each cause across repair-platform and forum data - a starting point for diagnosis, not a certainty.
What this should cost to put right
Across the causes listed above the repair runs $50 to $160. A quote far above the top of that range is usually a diagnosis of convenience - get a second opinion before you authorise it.
Repair it, or replace the unit?
This is the number people get wrong most often, and it costs them the most. Run the quote through the test - it uses the mid-point cost of the fix above against a new unit and the years this one has left.
REPAIR IT
The repair is 12% of a new unit and the appliance has roughly 4 year(s) of expected life left. Fixing it is the economical call. A new unit would save about $45/year in running costs, so keep repairing until that pays back in under 5 years.
Decision rule: repair when the fix costs under 50% of a replacement and the unit is under 70% through its expected life.
Other microwave symptoms
Common questions
Is it dangerous if my microwave has a "not heating and making loud noise" problem?
Usually not immediately - none of the likely causes on this page involve gas, fuel or a mains electrical fault. The two cautions that apply everywhere: keep water away from any electrical point, and if you ever smell gas or burning, stop diagnosing and call a professional.
How much does it cost to fix a microwave with a "not heating and making loud noise" problem?
Most fixes for this run $50 to $160. The most common cause, failed door interlock switch, runs about $50 to put right, and the part you would be looking for is interlock switch. Get the diagnosis in writing before authorising anything above the top of the range.
Why does my microwave have a "not heating and making loud noise" problem?
In about 34% of reported cases it is a failed door interlock switch. It is the first thing to check because it is the most common - and usually the cheapest. If that checks out clean, work down the ranked list on this page before paying for a diagnosis.
Should I repair or replace my microwave?
Repair it when the fix costs under half of a replacement and the unit is under 35% through its roughly 9-year expected life. Past that point a repair is usually a deposit on the next failure - run the test on this page with your actual quote before you decide.
How this figure was built
Reviewed 2026-08-28 · quarterly.
- Bureau of Labor Statistics, Occupational Employment and Wage Statistics - construction and repair trades
- EPA Energy Guide appliance ratings
- North American Electrical Metrics / manufacturer parts catalogues
National averages. Local labour can run 20-40% above or below these figures; the calculators apply a metro factor on top.
Full disclaimer · How we price