It runs but doesn't heat — magnetron, diode, transformer
The turntable doesn't turn — turntable coupler
The door won't latch — door interlock switch
The panel is dead — noise filter board, control panel assembly, line fuse
It sparks inside — magnetron, diode
The light won't turn on — lamp assembly
The auto or sensor-cook settings guess wrong every time — humidity sensor
Documented failures
Lamp assembly
Technician onlyVendor replaces this part if the microwave light will not work
Stop. DIY on models with an external or cavity-accessible lamp housing. If it's only reachable by removing the outer cabinet, stop and call a technician instead.
Try this first — it costs nothing. Nothing free here — a dead lamp assembly needs replacing.
Check, in this order
Confirm it's the lamp assembly itself and not the door switch or panel by checking whether the cavity stays dark with the door open and during a cook cycle both.
Parts exist for this component and are deliberately not listed here: this is not a repair to attempt yourself.
Worth fixing? Repair - the part is a small fraction of a new machine. Part $23.99 against $1,595.33 for a new machine (1.5%).Part cost only. A service call adds a regional diagnostic fee plus labour.
Door interlock switch
Technician onlyVendor replaces this part if the microwave will not run even when the door is closed
Stop. STOP. Licensed technician only.
No free first check for this one. There is no safe free check that gets closer to an interlock diagnosis than confirming the door closes firmly.
Check, in this order
Confirm the door itself closes firmly and the latch hooks aren't bent before assuming a switch has failed.
Note whether the unit won't start at all, starts and stops erratically, or runs with the door open — if the light or fan runs with the door open, unplug it immediately and treat that as a safety emergency, not a repair job.
Before you open anything
Unplug it and leave it unplugged — do not touch anything inside the cabinet.
Never bypass, jumper, or defeat a door interlock switch for any reason — it is the safety mechanism that stops the magnetron when the door opens, and defeating it can expose you to microwave radiation.
These switches are wired into the same compartment as the high-voltage capacitor on most models.
Parts exist for this component and are deliberately not listed here: this is not a repair to attempt yourself.
Worth fixing? Repair - the part is a small fraction of a new machine. Part $25.20 against $1,595.33 for a new machine (1.6%).Part cost only. A service call adds a regional diagnostic fee plus labour.
Line fuse
Technician onlyVendor replaces this part if the microwave is not working at all
Stop. STOP. Licensed technician only.
Try this first — it costs nothing. Test the outlet and breaker before assuming the fuse itself is blown.
Check, in this order
Test the outlet with another appliance first — a dead outlet or tripped breaker looks identical to a blown fuse.
Note whether the failure followed a pop, arcing, or a burning smell, which points at a diode or short rather than a simple overload.
Before you open anything
Unplug it before doing anything else.
The line fuse is reached by removing the outer cabinet cover, which exposes the high-voltage capacitor — this is not a simple bulb-style fuse swap.
A blown line fuse is a symptom of a high-voltage fault, not a simple part to swap and move on — replacing it alone without finding the underlying cause risks it blowing again, or worse.
Parts exist for this component and are deliberately not listed here: this is not a repair to attempt yourself.
Worth fixing? Repair - the part is a small fraction of a new machine. Part $5.79–$15.60 against $1,595.33 for a new machine (1.0%).Part cost only. A service call adds a regional diagnostic fee plus labour.
Turntable coupler
Usually DIYVendor replaces this part if the turntable will not spin
DIY. No tools beyond your hands are usually needed.
Try this first — it costs nothing. Just look at the coupler and tray notches first — this is usually a five-dollar plastic part, not a motor problem.
Check, in this order
Check the coupler's drive tabs for rounding or cracks — this is the single most common cause of a tray that sits still while the motor keeps running.
Confirm the tray's underside notches aren't worn smooth too.
Before you open anything
Unplug it before reaching into the cavity.
Tools
Phone camera ($0) — Photograph connector positions before unplugging anything.
The repair, in order
Unplug the unit and lift out the glass tray and roller ring.
Pull the old coupler off its spindle.
Press the new coupler on until it seats fully.
Replace the tray and roller ring and spin the tray by hand to confirm it engages.
How you know it worked. The tray turns continuously through a full cook cycle with no slipping.
Prices are a snapshot taken on the date shown and are not monitored. Check the retailer before buying.
Worth fixing? Repair - the part is a small fraction of a new machine. Part $45.97 against $1,595.33 for a new machine (2.9%).Part cost only. A service call adds a regional diagnostic fee plus labour.
Control panel assembly
Usually DIYVendor replaces this part if the microwave is not working at all
DIY once you've confirmed the fuse is good and the control board isn't the actual fault — a new panel assembly won't fix a board problem.
Try this first — it costs nothing. Wipe the keypad and reseat the ribbon connector — a loose ribbon causes exactly this symptom.
Check, in this order
Note whether some buttons work and others don't — partial response points at the panel assembly, total silence at the board or fuse.
Check the ribbon connector to the board is seated before replacing the whole assembly.
Before you open anything
Unplug it before opening the panel.
The membrane/keypad panel sits outside the sealed electrical compartment on most models — confirm that on yours before proceeding, since some combine the panel and control board behind one cover.
Tools
T20 Torx driver ($7) — Some control and door assemblies use Torx rather than hex.
#2 Phillips screwdriver ($6) — Panel and bracket screws.
Phone camera ($0) — Photograph connector positions before unplugging anything.
The repair, in order
Unplug the unit and remove the screws holding the panel assembly/bezel in place.
Photograph the ribbon and harness routing.
Swap the panel assembly and reseat the ribbon fully.
Reinstall the bezel and test every button before closing it up.
How you know it worked. Every button and indicator responds correctly and the display reads normally.
Prices are a snapshot taken on the date shown and are not monitored. Check the retailer before buying.
Worth fixing? Weigh it - this part is a meaningful share of a new machine. Part $323.46–$368.00 against $1,595.33 for a new machine (23.1%).Part cost only. A service call adds a regional diagnostic fee plus labour.
Magnetron
Technician onlyVendor replaces this part if the microwave is not working at all
Stop. STOP. Licensed technician only.
No free first check for this one. There is no safe free check that gets closer to a magnetron diagnosis than the water-cup test above.
Check, in this order
Confirm the turntable, light, and fan all still run normally — everything running but nothing getting hot is the classic magnetron/HV-circuit signature.
Run a full water-load cup once: it should get hot within 60-90 seconds on high.
Before you open anything
Unplug it and leave it unplugged — do not touch anything inside the cabinet.
The high-voltage capacitor next to the magnetron can hold a lethal charge for hours or days even after the unit is unplugged. Only a technician with a discharge tool should open this compartment.
Parts exist for this component and are deliberately not listed here: this is not a repair to attempt yourself.
Worth fixing? Repair - the part is a small fraction of a new machine. Part $31.99–$198.00 against $1,595.33 for a new machine (12.4%).Part cost only. A service call adds a regional diagnostic fee plus labour.
Diode
Technician onlyVendor replaces this part if the microwave is not working at all
Stop. STOP. Licensed technician only.
Check, in this order
Note whether the failure came with a pop, a blown fuse, or a burning smell — all three are useful detail for the technician.
Before you open anything
Unplug it and leave it unplugged — do not touch anything inside the cabinet.
A failed diode is a classic cause of a loud pop and a blown fuse, and it sits directly in the high-voltage circuit next to the capacitor.
Parts exist for this component and are deliberately not listed here: this is not a repair to attempt yourself.
Worth fixing? Repair - the part is a small fraction of a new machine. Part $12.20 against $1,595.33 for a new machine (0.8%).Part cost only. A service call adds a regional diagnostic fee plus labour.
Humidity sensor
Technician onlyVendor replaces this part if certain heating settings on the microwave will not work properly
Stop. STOP. Licensed technician only.
Try this first — it costs nothing. Switch to manual time and power as a workaround while you wait — it bypasses the sensor entirely.
Check, in this order
Note whether auto/sensor-cook settings consistently undercook or overcook compared with using manual time and power — that pattern points at this sensor.
Parts exist for this component and are deliberately not listed here: this is not a repair to attempt yourself.
Worth fixing? Repair - the part is a small fraction of a new machine. Part $195.00 against $1,595.33 for a new machine (12.2%).Part cost only. A service call adds a regional diagnostic fee plus labour.
Transformer
Technician onlyVendor replaces this part if the microwave is not working at all
Stop. STOP. Licensed technician only.
Check, in this order
Note whether there's any hum, buzz, or smell at all when it's plugged in and started.
Before you open anything
Unplug it and leave it unplugged.
A failed high-voltage transformer often shows up as a burning smell or a dead, silent unit with no hum at all — treat it exactly like magnetron work.
Parts exist for this component and are deliberately not listed here: this is not a repair to attempt yourself.
Worth fixing? Weigh it - this part is a meaningful share of a new machine. Part $268.00 against $1,595.33 for a new machine (16.8%).Part cost only. A service call adds a regional diagnostic fee plus labour.
Noise filter board
Technician onlyVendor replaces this part if the microwave is not running properly
Stop. STOP. Licensed technician only.
Check, in this order
Note whether the symptom is total power loss, interference with a nearby TV or radio, or a breaker that trips — all point at the noise filter board to a technician.
Parts exist for this component and are deliberately not listed here: this is not a repair to attempt yourself.
Worth fixing? Repair - the part is a small fraction of a new machine. Part $29.95 against $1,595.33 for a new machine (1.9%).Part cost only. A service call adds a regional diagnostic fee plus labour.
If you replace it instead
Configuration-matched to this machine (built-in, 27, ~1.4 cu ft). Prices are UPC-verified Amazon listings, not estimates. Like-for-like replacement rarely pays for itself on energy alone — replace for fit and features, or because the repair maths above says so.
A candidate must match this machine's configuration (style, fuel and defrost class) before price or efficiency is considered. Prices are a snapshot from the date shown; availability is not monitored — check the retailer before buying.