Thermador Oven Error Code E104

Error code E104 on a Thermador oven indicates that the temperature sensor for the upper or single oven cavity (designated as Converter 1, or Cvt 1) has developed a short circuit condition. The oven control board continuously monitors the resistance output of the cavity temperature sensor to determine actual oven temperature. When the sensor circuit reads an abnormally low resistance value consistent with a short, the board interprets this as a fault and locks out normal operation to prevent unsafe temperature conditions. A shorted sensor will typically cause the control to read falsely high temperatures or produce erratic readings.

The temperature sensor used in Thermador ovens is a negative temperature coefficient (NTC) or positive temperature coefficient (PTC) resistive probe mounted inside the oven cavity. A short circuit in this circuit can occur at the sensor probe itself, along with the wiring harness connecting it to the control board, or at the connector terminals. Physical damage, excessive heat exposure, pinched wiring, or moisture intrusion are the primary mechanisms that cause the sensor or its circuit to short.

The first diagnostic step for E104 is to refer to Diagram 2/4, which identifies the sensor location, connector pinouts, and wiring path for Cvt 1. Technicians should use a multimeter to measure resistance across the sensor terminals and compare those readings to the specified values for the sensor at a known ambient temperature. A reading at or near zero ohms confirms a short. If wiring checks out, the sensor probe itself should be replaced before suspecting the control board.