Bosch Dryer Error Code E18 — Heater Temperature Sensor Failure
What this means
The E18 error code on Bosch dryers indicates that the heater temperature sensor (NTC thermistor) has failed or is providing readings outside the expected range. This sensor monitors the heating element to prevent overheating. When it fails, the dryer cannot regulate heat properly and shuts down as a safety measure. The error can be caused by a faulty NTC sensor, damaged wiring, or a problem with the heating element itself causing abnormal temperatures.
Alternate codes: E:18
Step-by-step fix
4 stepsLocate the heater temperature sensor
Unplug the dryer. Remove the top panel and the back panel to access the heater housing. The NTC temperature sensor is a small probe or disc mounted on or near the heating element assembly, connected by two wires.
Take photos of all wire connections before disconnecting anything to ensure correct reassembly.
Test the NTC sensor
Disconnect the sensor wires and measure resistance with a multimeter at room temperature. A functioning NTC sensor should read approximately 10,000–12,000 ohms (10K–12K) at 25°C (77°F). An open circuit (infinite resistance) or very low resistance indicates failure.
NTC means Negative Temperature Coefficient — resistance decreases as temperature rises. At 50°C it should read around 4,000–5,000 ohms.
Inspect the wiring and connections
Follow the sensor wires from the heater housing to the main control board. Check for burned, frayed, or pinched wires. Inspect all connectors for corrosion or loose pins. Repair any damaged wiring with heat-shrink connectors.
High heat areas near the heater housing are prone to wire insulation breakdown. Replace any wire with cracked insulation.
Replace the sensor if faulty
If the NTC sensor reads out of specification, remove it from the heater housing (usually held by one clip or screw), disconnect the wires, and install the new sensor. Reconnect all wiring, reassemble the panels, and run a test cycle.
After replacing the sensor, monitor the first full drying cycle to ensure the dryer heats and cools properly without triggering the error.
When to call a professional
If the NTC sensor and wiring are both good but the E18 error persists, the heating element itself may be partially shorted, causing abnormal temperature spikes that the control board interprets as a sensor fault.
Related error codes
Information compiled from manufacturer service manuals, official troubleshooting documentation, and appliance repair industry resources. This guide is for informational purposes only — always consult a qualified technician for complex repairs.
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