Bosch Range Error Code F3

The F3 error code on a Bosch range indicates that the warming drawer temperature sensor is returning a resistance value outside of the expected range during either a self-test cycle or active use. The warming drawer uses a negative temperature coefficient (NTC) thermistor as its temperature sensing element. This thermistor changes resistance in a predictable, inverse relationship with temperature. When the control board reads a resistance value that falls outside the acceptable parameters for the current operating conditions, it flags the F3 fault and typically disables the warming drawer circuit to prevent uncontrolled heating.

The most common causes involve the thermistor itself, its wiring harness, or the connection points between the sensor and the control board. A failed or degrading thermistor may read an open circuit (very high resistance) or a short circuit (near-zero resistance), both of which trigger the fault. Similarly, damaged wiring, corroded terminals, or a loose connector plug can cause intermittent or incorrect resistance readings that the board cannot interpret as a valid temperature signal.

Because the F3 code specifically targets the warming drawer sensor circuit rather than the main oven sensor, diagnosis should be focused on the components located in and around the warming drawer assembly. Technicians should inspect the sensor wiring from the drawer compartment back to the main control board, check for pinched or melted wires near heat sources, and measure thermistor resistance with a multimeter to compare against the expected resistance curve at a known ambient temperature.