Error code
Thermador dishwasher error code E12
Thermador error code E12: hard water has left enough scale in the heat pump to change how it heats. What the code covers, what to check first, and what it does not tell you — on dishwashers.
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What we can confirm
Code E12, from the manufacturer's own documentation
A code is only meaningful together with the generation showing it — the same two digits mean different things across generations.
The code
E12
Hard water has left enough scale in the heat pump to change how it heats
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What it narrows down to
Limescale in the heat pump
What you are probably seeing
Diagnostic
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What it looks like from the kitchen
The symptom this code usually arrives with
A code names the subsystem; the symptom is what sent you to look at the display in the first place. That page says what it usually turns out to be, cheapest cause first.
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Often the water, not the machine Dishwasher not cleaning properly
Grit left on plates, a film on glasses, or detergent still sitting in the cup at the end. On hard water most of this is chemistry and loading before it is ever a part.
- Grit or food left on the lower rack
- A cloudy film on glassware
- Detergent still in the dispenser afterwards
In more detail
About Thermador dishwasher error code E12
What this one means
Hard water has left enough scale in the heat pump to change how it heats. It is a code the manufacturer publishes for this appliance, not one we have worked out — and it is decoded here rather than left as three characters on a display.
The other ways your machine may say it
The same condition is published under more than one label, because it has been carried across generations of this appliance:
- E12, E2060 — the same condition, on machines of different ages
What the code covers
A published cause names a circuit rather than a component, which is the single most useful thing to know before ordering a part. This one covers:
- The heat pump's heat exchanger
- The water softener, if it is empty of salt
- Months of South Florida water
What to try yourself
- Run a descaler through an empty machine
- If the machine takes softener salt, refill it — the reservoir is in the tub floor
Then what
Miami-Dade water is hard enough that this is maintenance rather than a failure. It comes back if the salt stays empty.
This code is published for dishwashers. The full list of codes has the rest of them, searchable, including the labels older and newer machines use for the same conditions.
This article is based on:
- Official manufacturer documentation
- Internal repair procedures
- Technician repair history
- Company quality standards