The short answer
Start from the thermostat or control reading wrong: on a Thermador freezer that is the likeliest explanation for what you are looking at, and a sealed-system or compressor fault is the least likely. Most of this you can settle before anyone is called.
What the symptom looks like
- Food is soft and the unit is plainly running — The compressor is working and the cabinet is not getting the benefit.
- A heavy frost sheet on the walls or the rear panel — Ice where air should be moving. That is a closed air path, not a failed system.
- NEAR MISS: the unit is silent and the light is dead — No power. That is a different fault and a different page.
Causes ranked for this brand, likeliest first
- The thermostat or control reading wrong — The unit acts correctly on a wrong number, so it either stops calling for cooling or calls for it without pause. It leads on Thermador: a board decides the behaviour rather than a switch, so a control fault reads as a machine declining to act.
- A blocked condenser or no clearance around the cabinet — The heat removed has to go somewhere. A furred coil or a unit jammed into an alcove cannot shed it. Second here: a built-in cavity vents through a path the cabinet defines, and that path blocks before anything else does.
- Frost build-up closing the air path — On a frost-free unit a stalled defrost ices the evaporator and the air stops. On a manual unit the ice simply insulates. Third: everything this appliance does depends on air moving where the designer intended it to.
- A sealed-system or compressor fault — Lost charge or a compressor that no longer pumps. The unit runs and nothing anywhere gets cold. Last, and the order is the point: it is the least common cause here and the only one that is not an owner fix.
The order to work in
- Check the set point, then power-cycle the unit — A latched control state and a failed control look the same and one of them is free.
- Check the air gap around the cabinet and the state of the coil — Two things, one cause: heat that cannot leave.
- Look at how much ice is actually in there — A heavy build-up is the cause and not the consequence, whatever the unit's badge says.
What an owner can safely check
- Read the set point, then switch the unit off at the wall for a few minutes and back on — A freezer holds food safely at 0 degrees F (-18 degrees C) or below, so set it there and judge from that.
About 15 min
- Vacuum the condenser coil and make sure there is a real air gap at the back and sides — A garage or alcove install is where this one hides.
Tools: a vacuum, a soft brushAbout 30 min
- Empty the freezer, switch it off and let it defrost completely with the door open — On a manual-defrost unit this is maintenance. On a frost-free one it is a diagnosis.
About 90 min
- STOP HERE: past this point needs gauges on the sealed system — Licensed work, and the end of the owner checks.
Before you open anything
Safety
Unplug the appliance or switch off its breaker before removing any panel. A capacitor can hold a charge after the power is off. Get help before pulling the cabinet out: a loaded unit runs away from you on a hard floor and the supply line behind it tears easily. Never open sealed-system tubing.
When to call a technician
Call once the seal passes, the coil is clean, a full defrost is done and the unit still will not hold temperature. Call immediately for oil near the compressor or a burning smell. A freezer holds food safely at 0 degrees F (-18 degrees C) or below: if the contents have been above that for hours, that is a decision to make now.
Nearest pages of this class
What this page leaves to a more specific one
This page is written for the Thermador freezer as a class, not one family or model line. Where a family-specific page exists it is linked below and it is the more specific answer. Deliberately not here: defrost heater specifications, thermostat part numbers and family-specific service sequences.
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
