Thermador · Microwaves
Thermador Microwave and Speed Oven Repair
Thermador microwave drawers, built-in microwaves and speed ovens, plus the older 27-inch units that stack a microwave over a warming drawer and an oven, and the CM ovens (the CM301 single and the upper cavity of the CM302 double) that combine microwave with convection and baking heat. A microwave that runs without heating, a fuse that keeps blowing, a drawer that will not move or a panel that ignores you are the usual calls.
$79 service call, applied to the repair. Monday to Saturday, 8 AM to 7 PM.
- $79service call, applied to the repair you approve
- In-housesealed-system work: compressors, evaporators, leaks
- Since 2022CA BHGS #50388, EPA-certified
- 90 daysno-fee return visit if the same fault comes back
In short: a microwave that lights, turns and hums but leaves food cold usually has a fault on the high-voltage side. One that goes completely dead often has a blown fuse, and that fuse usually blew because a door switch is worn or out of line. On drawers, the drive and its position switches come first. Never open the cabinet yourself: the high-voltage parts hold a dangerous charge even unplugged.
Which Thermador microwave you have
- Microwave drawers. 24 and 30 inch drawers under a counter, in an island or below a wall oven, opening and closing on a motor at a touch.
- Built-in microwaves. A microwave in a wall cabinet or above a wall oven, finished with a trim kit.
- Speed ovens. A microwave with a convection element, a fan and a broil element, so it browns and bakes as well as heating. Built in alone or as the top half of a combination with a wall oven.
- The 27-inch SMW272. A modular unit from around 2000: a microwave section on top, a warming drawer in the middle and an S-series convection oven at the bottom. The microwave, rated at 1100 watts with an inverter power supply, slides out of its enclosure from the front, so the microwave and the warming drawer are serviced without pulling the unit from the wall.
- CM combination ovens. The single CM301 and the upper cavity of the CM302 double combine microwave with convection and regular baking heat. Its microwave parts live in the top plenum of the oven. The oven side is covered on Thermador wall oven repair.
On most microwave drawers the rating plate is visible with the drawer fully open; on the SMW272 it is near the oven controls above the microwave section. A photo of the model and serial lets us bring the right parts.
How a built-in microwave works
- Making the heat. A magnetron turns high voltage into microwave energy. Older units build that voltage with a transformer, a capacitor and a diode; inverter units such as the SMW272 use an electronic power board instead. The capacitor or inverter can stay charged after the power is cut.
- Spreading it. A turntable or a stirrer blade at the top of the cavity spreads the energy. In the CM upper oven the stirrer also stirs the hot air.
- The safety chain. Two or three door switches must agree before the high voltage is allowed on. The monitor switch exists to blow the fuse on purpose if a primary switch sticks closed while the door opens, so a blown fuse is a message, not the fault itself.
- Cooling and cutouts. A fan keeps the magnetron and power parts cool, and a thermal cutout on the magnetron stops the oven if it overheats. On the CM ovens an air switch proves the transformer fan is running, and if it does not close, the upper oven shows F34.
- Sensing and controls. A steam or humidity sensor times the sensor cook and reheat modes from the vapor food gives off. The touch panel, control board and, on drawers, the drive motor, gear rack and position switches complete it.
What fails on a Thermador microwave, most common first
Runs but does not heat
What it usually is: the magnetron, the high-voltage transformer or inverter board, the capacitor or diode on older units, or a magnetron thermal cutout that opened because cooling air was blocked or the fan slowed.
What you can check: heat a cup of water for one minute on full power. If it barely warms, stop using the microwave. Make sure nothing blocks the vents around the trim.
What we do: drain the stored charge, test each high-voltage part with the power off, and replace the failed one. Our job post GE Monogram Microwave Not Heating: Magnetron Fix (Orange County, July 2026) had this symptom and needed a magnetron; a Thermador gets the same tests.
Completely dead, or the fuse keeps blowing
What it usually is: a door or latch switch that is worn or out of line, so the monitor switch blows the fuse, or a short in the high-voltage circuit. A new fuse alone just blows again.
What you can check: the breaker, and whether the clock still shows. Look for a door that sags or does not close flush.
What we do: test every switch in the safety chain, replace worn switches rather than adjust them, check door alignment, then fit the fuse and run a leakage test.
Drawer will not open, close or stops partway
What it usually is: something in the drawer track, a worn drive gear or rack, the drive motor, a position switch, or the control. Pushing or pulling the drawer by hand can strip a gear.
What you can check: crumbs or a utensil in the guides, and the control lock. Use the touch pads only, and do not lean on an open drawer.
What we do: slide the drawer out onto padding, test motor, gears and switches, and replace what failed. More on microwave drawer repair.
Panel ignores you, or shows nothing useful
What it usually is: a child or control lock, a demo mode on models that have one, a worn touch panel, a loose ribbon cable or a failed control board. On these controls a pad that does not beep was not accepted.
What you can check: the lock (on the SMW272 it sits under the Function pad), and switch the breaker off for a minute and back on.
What we do: test the touch panel and board, and replace the one that failed.
Sensor modes stop early or run long
What it usually is: a humidity sensor coated with grease or failed, or a load too small to give off much vapor.
What you can check: clean the cavity and vents, and compare a timed cook with a sensor cook.
What we do: test the sensor and its circuit, and replace it if it reads wrong.
Speed oven not browning, or noisy fan
What it usually is: an open convection or broil element, a convection fan with worn bearings, or a thermal cutout. The microwave side can keep working while the convection side has failed, and the reverse.
What you can check: which modes still heat: microwave alone, convection alone, and the combined modes.
What we do: measure the elements and the fan motor and test the cutouts, then replace the failed part.
Warming drawer cold on an SMW272
What it usually is: the drawer's own thermostat, on-off switch or heating element; worn slides make it stick.
What you can check: that the drawer is switched on and pushed fully closed.
What we do: lift the drawer off its slides, test the parts and replace the failed one, all from the front.
Stay safe. Never remove the outer cabinet of a microwave: the capacitor or inverter can hold a lethal charge even unplugged. Do not run it empty, with a damaged door or seal, or with metal inside, and stop using it if you see sparks or the door does not close flush. After any door, latch or magnetron repair we check for microwave leakage with a meter before you use it again.
Repair or replace a Thermador microwave
| What failed | Our usual advice |
|---|---|
| Door switches, fuse, thermal cutout, drive gear, light, sensor or turntable motor | Repair. Inexpensive parts on a built-in that would cost far more to replace and re-trim. |
| Magnetron, inverter board or control board | Usually repair on a drawer, speed oven or combination, once the part and its lead time are confirmed. |
| Magnetron plus a board on a 20-year-old SMW272 or CM oven, or parts no longer made | Consider replacing. A new unit must fit the existing cutout and trim, so measure first. |
What a Thermador microwave repair costs
The service call is $79, and it is applied to the repair when you approve the written price. Common parts such as door switches and fuses are usually on the van; a magnetron or board for an older SMW272 or CM oven can take longer, and we tell you the lead time first.
Microwave drawer and speed oven repair
| Repair | Typical price, parts and labor |
|---|---|
| Drawer motor or drive mechanism | $400 to $800 |
| Door switch set | $300 to $550 |
| Magnetron | $450 to $800 |
| Control board | $550 to $1,000 |
Typical Orange County ranges for parts and labor. The $79 service call is applied to any of them. Parts that ship from the manufacturer and older or discontinued models can run higher. You get the exact written price after the diagnosis and before any work starts.
See also wall oven and speed oven repair, pricing, Thermador ranges, and every line on Thermador repair.
Talk to the technician first
Monday to Saturday, 8 AM to 7 PM. The $79 service call is applied to the repair.
Thermador microwaves: questions
My Thermador microwave runs but the food stays cold. What failed?
Most often the magnetron. We test it and the parts that feed it before quoting, and on a built-in the repair usually costs less than replacing and re-trimming.
Why does my Thermador microwave keep blowing its fuse?
The fuse is part of the door safety chain and blows on purpose when a door switch sticks or is out of line. The switches and door alignment have to be fixed, or the new fuse blows too.
The oven door locks when I use the microwave on my CM combination. Is that normal?
Yes. On the CM ovens a motor latches the upper door when a microwave mode starts, and the microwave only runs once the latch confirms it. If the door will not latch, the microwave will not start.
Can you repair the microwave in my 27-inch Thermador SMW272?
Yes. Its microwave section slides out of the enclosure from the front, so the unit stays in the wall. On a unit this age we confirm the part is still available before quoting.
Do you repair Thermador speed ovens?
Yes, both sides: the microwave parts, and the convection element, broil element and fan that let it bake and brown.
Can I replace a microwave magnetron myself?
No. Reaching it means opening the high-voltage compartment, and the reassembled door and seals must pass a leakage test. It is a job for a technician with the right meter.