Bosch Dryer Error Code 3

Error code 3 on a Bosch dryer indicates a fault with NTC R2, the heater air temperature sensor. This thermistor monitors the temperature of the air entering or exiting the heater assembly, and the dryer's control board uses its resistance readings to regulate the heating cycle. When the board detects a resistance value outside the expected operating range, either too high (open circuit) or too low (short circuit), it flags error code 3 and signals the fault by flashing the Cupboard Dry LED in the progress indicator.

NTC thermistors change resistance predictably as temperature changes. A properly functioning NTC R2 will show a specific resistance at room temperature, and that value will decrease as temperature rises. If the sensor reads an implausibly high resistance, the circuit is likely open due to a broken wire or failed thermistor. If resistance is near zero, a short in the sensor or wiring is probable. Either condition prevents accurate heater air temperature monitoring, which is a safety-critical function, so the dryer shuts down.

Diagnosis follows the same procedure used for Error 1 (NTC R1). Technicians should inspect the NTC R2 sensor itself, the connecting cable along its full length, and the plug-and-socket connection at both the sensor end and the control board end. Resistance testing with a multimeter at room temperature, combined with a visual inspection for chafed insulation, corrosion at connectors, or physical damage to the sensor body, will typically identify the root cause.