Bosch Dryer Error E09 — What It Means & How to Fix It

What Does This Error Mean?

Error E09 means the NTC thermistor (temperature sensor) inside the dryer has reported a fault or is reading a temperature outside the expected range. The dryer uses this sensor to monitor heat levels and control the drying cycle safely. E09 requires a technician to test and replace the thermistor — but clean the condenser first as blockages can cause false temperature readings.

Affected Models

Bosch WTW87565GB
Bosch WTH84000GB
Bosch WQB145B0GB
Bosch WTW876H0GB
Bosch Serie 8 Heat Pump Dryer

Common Causes

NTC thermistor has failed and is sending out-of-range resistance readings
Wiring connector to the thermistor has come loose or corroded
Condenser blockage is causing genuine overtemperature that triggers E09
Thermistor has been physically damaged by heat or vibration
Control board fault is misinterpreting a valid thermistor signal

How to Fix It

Clean the condenser and lint filter thoroughly — blocked airflow causes genuine overheating that triggers E09.

Run a short cycle after cleaning — if E09 clears, the sensor was responding to real heat, not a sensor fault.
Unplug the dryer for 10 minutes to let it cool completely, then restart.

If the dryer genuinely overheated, a cool-down period resets the thermal sensor.
Check that the dryer is not in a confined space — adequate ventilation around the dryer is required.

Heat pump dryers need at least 10cm of clearance on all sides and good room ventilation.
Check the wiring connector on the thermistor — it is usually located near the heating element or exhaust duct.

A loose connector causes an open-circuit reading that the control board interprets as a fault.
Test the thermistor with a multimeter set to resistance — a healthy NTC thermistor reads 8,000–12,000 ohms at room temperature.

An open circuit (infinite resistance) or short circuit (0 ohms) confirms a faulty thermistor needing replacement.
Contact Bosch service or a qualified appliance engineer to replace the thermistor if testing confirms it is faulty.

Provide the full model number from the rating plate inside the dryer door for correct part identification.

When to Call a Professional

E09 ultimately requires a technician to test the thermistor with a multimeter and replace it if faulty. Thermistor replacement is relatively inexpensive ($20–$80 in parts) but requires opening the dryer. Always clean the condenser and filter before calling out a technician — blocked airflow causes genuine overtemperature that triggers E09.

Frequently Asked Questions

What is an NTC thermistor and why does it cause E09 on a Bosch dryer?

NTC stands for Negative Temperature Coefficient — a type of resistor whose resistance decreases as temperature rises. The dryer's control board reads this resistance to calculate the exact temperature inside the drum. When the thermistor fails, the board receives a reading it cannot make sense of and displays E09 as a safety stop.

Can a Bosch dryer thermistor be replaced DIY?

Technically yes — thermistors are inexpensive parts that clip or screw into place. However, accessing the thermistor requires opening the back or side panel of the dryer. If you are comfortable with basic appliance repair, there are model-specific guides online — always unplug first.

Will E09 come back after replacing the thermistor?

Not if the thermistor was the root cause and the condenser is kept clean. If E09 returns after a new thermistor, the control board may be misinterpreting the signal — that is a more expensive repair. Ensure the condenser and filter are cleaned regularly to prevent genuine overtemperature readings.