Direct answer: A Thermador oven that will not heat is usually dealing with one of three things: missing power to the heating circuit, a failed oven igniter or oven heating element, or an oven sensor problem that keeps the control from heating normally.
Most likely: Start with the basics you can see: confirm the clock and controls are alive, make sure it is not in a delayed or demo-style mode, verify the door is fully closing, and then watch what happens when you call for Bake. A gas oven that clicks or glows but never lights points toward the oven igniter. An electric oven with a cold or visibly split bake element points toward the oven heating element.
Separate the lookalikes early. If the display is dead, you may have a power problem instead of a heating problem. If the panel works but the cavity stays cold, watch and listen during the first minute of a Bake cycle. Reality check: most no-heat calls end up being a heating part, not a fancy electronics failure. Common wrong move: replacing parts because the broil still works without checking whether the bake side is the one that actually failed.
Don’t start with: Do not start by ordering an oven control. Controls do fail, but they are not the first bet when an oven simply will not heat.
The control panel responds and you can start a cycle, but the oven cavity never really warms up.
Start here: Start with the heating pattern check so you can tell whether the bake side, broil side, or gas ignition side is missing.
Food takes much longer than normal, preheat drags on, or the oven tops out well below the set temperature.
Start here: Check for a weak bake element, a weak oven igniter, or a sensor reading problem before blaming the control.
The upper heat comes on, but normal baking does not heat the oven properly.
Start here: Focus on the bake circuit first because that usually points to the oven heating element, oven igniter, or related wiring on the bake side.
You start Bake or Broil and get no heat response at all.
Start here: Confirm power, settings, and door closure first, then move to sensor or control-side diagnosis only after the simple checks are ruled out.
A tripped breaker, partial power loss, wrong mode, delayed start setting, or an oven door not closing fully can make the oven look dead or keep it from heating correctly.
Quick check: Make sure the display is normal, the time is set, no delay cycle is active, the breaker is fully reset, and the door closes snugly.
If you hear clicking, smell a little gas, or see a weak glow without ignition, the oven igniter is the usual culprit. A weak igniter can glow and still fail to open the gas valve properly.
Quick check: Start Bake and watch through the lower panel area if visible. A healthy igniter should glow strongly and the burner should light shortly after.
A broken or grounded bake element is one of the most common reasons an electric oven will not heat or only heats on broil.
Quick check: Look for blistering, a split, a burned spot, or a section that never glows when Bake is on.
If the heating parts look normal but the oven starts and stops oddly, overheats slightly then quits, or never calls for heat, the oven sensor can send the wrong temperature reading. Control failure is possible but not the first call.
Quick check: If both bake and broil fail with normal power present and no obvious heating-part failure, the oven sensor becomes a stronger suspect.
A lot of ovens get called dead when the real problem is partial power, a canceled cycle, a delay setting, or a door that is not closing all the way.
Next move: If the oven starts heating normally after a reset or setting correction, you likely had a power or control-setting issue rather than a failed part. If the panel works but the oven still does not heat, move on and watch how it behaves during a fresh Bake cycle.
What to conclude: You have ruled out the easy misses and can now focus on whether the oven is failing to create heat or just failing to start the heating sequence.
The next move depends on what kind of heat source your oven uses. Gas and electric no-heat symptoms look similar from the kitchen, but the failed parts are different.
Next move: If you clearly identify that only one heating side is missing, you have narrowed the repair to the bake element, igniter, or sensor side instead of guessing at the whole oven. If you cannot tell what is happening or both Bake and Broil stay dead, keep going with a visual inspection and sensor check.
What to conclude: A gas oven that glows but will not light usually needs an oven igniter. An electric oven with broil working but no bake heat usually points to the oven heating element or bake-side wiring.
Heating parts often tell on themselves. A burned bake element or a weak igniter can often be identified without deep teardown.
Next move: If you find a visibly damaged oven heating element or a clearly weak non-lighting oven igniter, you have a solid repair direction. If the heat source looks normal and there is no obvious wiring damage, the oven sensor becomes the next sensible check.
When the oven starts a cycle but never heats correctly and the main heating part is not obviously failed, the oven sensor is the next common part in line. It is a much better bet than jumping straight to the control.
Next move: If the sensor tests bad or shows obvious damage, replacing the oven sensor is the right next move. If the sensor checks out and the heating parts are not the issue, you are down to wiring or control-side diagnosis, which is where many homeowners should stop.
By now you should have enough evidence to make a smart repair choice. This is where you either replace the clearly failed oven part or call for service instead of throwing expensive electronics at it.
A good result: If the oven reaches temperature normally and cycles heat on and off without error, the repair path was correct.
If not: If the new part does not change the symptom, do not keep buying parts. The problem is likely wiring, connection damage, or a control issue that needs deeper diagnosis.
What to conclude: The common repair parts are now covered. If the oven still will not heat, the remaining fault is no longer the easy, high-probability DIY fix.
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If the panel lights up but the oven stays cold, the usual causes are a failed oven igniter on a gas oven, a failed oven heating element on an electric oven, or an oven sensor problem. Start by watching what happens during Bake instead of guessing at the control.
Yes. That is very common on gas ovens. A weak oven igniter can glow but still not draw enough current to open the gas valve properly, so the burner never lights.
Not always, but it usually means the oven still has at least some power and control function. When broil works and bake does not, the bake side heating part is a much stronger suspect than the control.
On an electric oven, look for a split, blister, burned spot, or a section that never glows during Bake. If the oven heats from the top on Broil but not from the bottom on Bake, the oven heating element moves way up the list.
Replace the oven sensor first only if testing or symptoms support it. Do not jump straight to the control unless the common heating parts and sensor have been ruled out, because controls are less common and more expensive guesses.
It can make baking weak or slow, but it usually does not cause a true no-heat condition by itself. Think of the oven door gasket as a secondary issue unless you also see obvious heat leaking around the door.