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Error code reference

Thermador Cooktop Error Code Ci4

Inductor NTC defective due to NTC not connected or NTC failure.

Thermador codesThermador cooktop codes

Inductor NTC defective due to NTC not connected or NTC failure.

First step from the service manual

Use the technical service menu to identify which inductor is defective. Connect NTC or replace NTC.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What Ci4 means on a Thermador cooktop

The Ci4 error code on a Thermador induction cooktop indicates a fault with the NTC (Negative Temperature Coefficient) thermistor associated with one of the induction coil inductors. The NTC thermistor is a temperature-sensing resistor whose resistance decreases predictably as temperature rises. The cooktop's control board continuously monitors this resistance to track inductor temperature and prevent overheating. When the board detects a reading outside the expected resistance range, whether because the NTC circuit is open, shorted, or completely disconnected, it throws the Ci4 fault and disables the affected cooking zone.

The two primary causes are a disconnected NTC connector and an outright NTC component failure. A disconnected NTC presents as an open circuit, which the control board interprets as an extreme or invalid temperature reading. A failed NTC thermistor can produce a fixed resistance value, a short to ground, or an erratic signal, all of which trigger the same fault code. Because multiple inductors are present in the cooktop, the Ci4 code does not automatically identify which zone is affected.

Diagnosis requires accessing the technical service menu built into the cooktop's control system, which can isolate the specific inductor generating the fault. Once the defective zone is identified, a technician should physically inspect the NTC connector for looseness, corrosion, or damaged wiring before condemning the thermistor itself. If the connector is secure and wiring is intact, the NTC thermistor should be tested with a multimeter and compared against the expected resistance curve for the component. A failed NTC will require replacement to restore normal operation.

Source: manufacturer service documentation.

Common causes of Ci4

  1. 01

    Disconnected NTC connector

    Wiring / connection

    Vibration or previous service work can cause the NTC thermistor connector to come loose from its socket on the inductor assembly or control board. Inspect all NTC wiring harness connections for the affected zone and reseat any disconnected plugs.

  2. 02

    Failed NTC thermistor

    Part replacement

    The NTC thermistor itself may have failed due to heat exposure, age, or electrical stress, producing an out-of-range resistance reading. Testing with a multimeter will show either an open circuit, a short, or a resistance value that does not correspond to the component's expected temperature curve.

  3. 03

    Damaged NTC wiring harness

    Part replacement

    The wiring between the NTC thermistor and the control board can develop breaks, chafing, or burn damage, particularly near the inductor where heat is highest. A visual inspection and continuity test of the wiring run will confirm whether the harness is the source of the open or intermittent circuit.

  4. 04

    Corroded or burnt connector pins

    Wiring / connection

    Even if the connector is physically attached, oxidized or heat-damaged pins can create high resistance in the NTC circuit and produce a fault. Inspect the connector terminals under magnification for discoloration, pitting, or carbon deposits.

  5. 05

    Control board sensing circuit fault

    Part replacement

    In less common cases, the input circuit on the control board responsible for reading the NTC signal can fail, causing the board to misread a functioning thermistor as defective. This is typically identified after confirming that the NTC thermistor and wiring both test within spec.

See the test procedure for each cause

Frequently asked questions about Ci4

What does Ci4 mean on a Thermador cooktop?
Ci4 indicates that the NTC thermistor for one of the induction inductors is either disconnected or has failed. The NTC thermistor is a temperature sensor the cooktop uses to monitor the heat level of each induction coil. When the control board cannot read a valid signal from this sensor, it disables the affected zone and displays Ci4. The technical service menu can be used to identify which specific inductor is generating the fault.
Can I fix the Ci4 error myself, or do I need a technician?
If the fault is simply a loose connector, a confident DIYer comfortable working inside an appliance can reseat the NTC wiring harness after disconnecting power. However, reaching the induction components typically requires disassembling the cooktop, and replacing a failed NTC thermistor or damaged wiring harness is more involved work. If you are not comfortable with appliance disassembly or electrical testing, a qualified technician is the safer choice.
Is it safe to keep using the cooktop when Ci4 is displayed?
The cooktop disables the affected induction zone when Ci4 is active, specifically because it cannot monitor that burner's temperature without a functioning NTC sensor. You should not attempt to use the faulted zone. Other zones may still operate normally, but the underlying fault should be repaired promptly to restore full safe functionality.
Will resetting the cooktop clear the Ci4 error code?
Cycling power may temporarily clear the display, but the Ci4 code will return as soon as the control board attempts to read the NTC again during operation. A reset does not address the disconnected connector or failed thermistor that is causing the fault. The underlying hardware issue must be resolved for the error to be permanently cleared.
How much does it cost to repair a Ci4 error on a Thermador cooktop?
Repair costs vary depending on the root cause. If the fix is simply reconnecting a loose NTC connector, a service call fee is the primary expense, typically in the range of $75 to $150. If the NTC thermistor itself needs replacement, parts and labor together generally fall in the range of $150 to $350, depending on your location and the technician's rates. A control board replacement, if needed, would cost more and could range from $300 to $600 or higher.

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