Older Thermador Cooktop c1 on CIT365DS and CIT304E Induction Models: Supply Voltage Too Low

What c1 means

Older CIT365DS and CIT304E induction cooktops show a lowercase c1 when the power voltage is too low. The manual prints this in the same table as the F codes. The cooktop stops heating because it is not getting enough supply voltage, which may come from the house wiring or the utility rather than the cooktop itself. The manual suggests a short off-and-on and, if it persists, contacting the electricity supplier.

Usual causes of c1

Low supply voltage at the cooktop
Loose or worn connection in the feed to the cooktop
Heavy load on the circuit lowering voltage
Cooktop reading voltage incorrectly

✓ A safe check worth trying

1. Turn the cooktop off. 2. Wait a few seconds, then turn it back on. 3. If c1 stays, note whether lights or other appliances dim at the same time. 4. If it continues, contact the electricity supplier, and call us to check the cooktop's feed and connections.

! Why you should stop here

Voltage and connections must be measured live, which is not a home job.
Loose supply wiring at an induction cooktop can overheat terminals.
We check the cooktop side and give a written price; utility issues go to your supplier.

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.

→Same appliance

More Cooktop codes

F1Thermador Induction Cooktop F1 / F6 Error Code c2 / c3Legacy Thermador Cooktop c2 / c3 on CIT365DS and CIT304E Induction Units: Element Overheated, Deactivated F9Thermador Induction Cooktop F9 Error Code (Flex Zone) U400Older Thermador Cooktop U400 on CIT365DS and CIT304E Induction Models: Cooktop Connected Incorrectly U400Thermador Cooktop U400 Voltage Error Code E7015Thermador Cooktop E7015 on Current Masterpiece and Freedom Induction Models: Electronics Overheated E8207Thermador Cooktop E8207, Current Masterpiece and Freedom Induction: Zone Shut Off, Electronics Hot E8208Thermador Cooktop E8208 on Current Induction Models (Masterpiece/Freedom): Overheated Electronics

c1c1 questions

Is c1 a cooktop failure?

Not necessarily. The manual defines c1 as low power voltage, so the cause may be in the supply. A technician measures the voltage at the cooktop to separate the two.

Why a lowercase c?

The glyphs on the printed table show c1, c2 and c3 with a lowercase c. If your display looks like that, you are reading this older CIT365DS or CIT304E table.

Who should I call first?

If the code remains after a reset, the manual says to contact the electricity supplier. If the supply tests normal, we inspect the cooktop and its connection with a written quote.