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Error code · Cooktop

Older Thermador Cooktop U400 on CIT365DS and CIT304E Induction Models: Cooktop Connected Incorrectly

U400 on an older CIT365DS or CIT304E induction cooktop means the cooktop is connected incorrectly. Current Thermador induction cooktops use U400 differently, so this is the older table's meaning only. It usually appears after installation, a…

Serious · switch off and call
Code
U400
Appliance
Cooktop
Brand
Thermador
Warranty
30-day workmanship

What U400 means

U400 on an older CIT365DS or CIT304E induction cooktop means the cooktop is connected incorrectly. Current Thermador induction cooktops use U400 differently, so this is the older table's meaning only. It usually appears after installation, a move, or electrical work. The manual's remedy is to disconnect at the breaker or fuse, check the connection, reconnect, and call customer service if U400 returns.

Usual causes of U400

  • Incorrect wiring or phase connection at the cooktop
  • Loose or swapped supply conductors
  • Recent installation or electrical work done improperly
✓ A safe check worth trying

1. Turn the cooktop off. 2. Switch off its circuit breaker or fuse before doing anything else. 3. Do not open wiring yourself; just confirm the cooktop's connection was not recently disturbed. 4. Restore power; if U400 appears again, leave it off and call for service.

! Why you should stop here
  • Checking the wiring means working on the home's 240-volt supply, which is dangerous.
  • A wrong connection can damage the cooktop's electronics.
  • We inspect the connection and quote in writing before changing anything.
Taking off a panel yourself does not by default void a manufacturer warranty, yet it can lead to accidental damage, and some manufacturers attach their own service terms. Read your warranty paperwork, or ask us, before you decide.
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U400U400 questions
Why did U400 appear after a kitchen remodel?

The manual says the cooktop is connected incorrectly. New wiring, a moved cooktop, or a changed breaker can cause it, so the connection should be checked by a qualified person.

Can I just reset the breaker?

The manual does suggest disconnecting at the breaker or fuse and checking the connection. But if U400 comes back, it is a wiring matter and you should call customer service.

Is U400 the same on newer Thermador cooktops?

No. Current Thermador induction cooktops have their own U400 page and meaning. This one covers the older CIT365DS and CIT304E display, so check your model first.

Request service

Is U400 still showing?

Our technician checks it in your home and hands you a written price before touching anything.