Bosch WTG90 Dryer Not Stopping After Load Detection

Understanding the Problem
A Bosch WTG90 dryer that refuses to stop after load detection can be both frustrating and a safety concern. The dryer’s load sensor is designed to detect the presence of clothes and adjust the drying cycle accordingly. When the sensor fails or the control logic malfunctions, the dryer may run continuously, exhausting energy and damaging garments. This article walks through common causes, diagnostic steps, troubleshooting tips, and preventive measures to get your Bosch WTG90 back to working order.

The Load Detection Feature
The load sensor in the Bosch WTG90 uses a small metal strip that generates a signal when clothes touch it. The control board interprets this signal and determines when to start or stop the drying cycle. If the sensor or the associated circuitry is compromised, the dryer may interpret that clothes are still present and keep running.

Common Causes of the “Not Stopping” Issue

• Faulty Load Sensor – Wear or contamination can cause the sensor to stay “active.”
• Worn or Damaged Thermistor – The thermostat monitors temperature; a stuck high‑temperature reading can keep the dryer running.
• Malfunctioning Control Board – A glitch in the firmware or damaged board may misread sensor signals.
• Clogged or Blocked Vent – Poor airflow increases temperature; the dryer may continue to cycle to achieve a safe temperature.
• Electrical Wiring Issues – Loose connections, frayed wires, or blown fuses can prevent the stop signal from reaching the motor.

Diagnostic Steps

1. Check the Load Sensor – Inspect the sensor strip for dirt or damage. A clean, intact strip usually appears as a narrow, white metallic line on the drum interior.
2. Verify the Thermistor – Use a multimeter to test the resistance. A proper reading should match the manufacturer’s spec sheet.
3. Examine the Vent Path – Open the back of the dryer and the vent pipe. Remove lint and debris, ensuring a clear airflow path.
4. Inspect Wiring – Look for loose connectors, frayed cables, or burnt insulation near the control board and motor.
5. Look for Error Codes – The Bosch WTG90 displays error codes on the front panel. Note any digits that appear during the malfunction.

Troubleshooting the Load Sensor

• Cleaning – Remove the sensor strip gently with a soft brush or cotton swab.
• Replacement – If the strip is bent or broken, replace it with a Bosch OEM part.
• Testing – After cleaning or replacement, run a short cycle to confirm the sensor reads “no load” when the drum is empty.

Common Troubleshooting for the Thermistor

• Calibration – Some models allow thermistor calibration via a reset sequence on the control panel.
• Replacement – If the thermistor reads a constant high value, swap it with a new unit.

Resetting the Control Board

1. Power Cycle – Unplug the dryer for 30 seconds, then plug it back in.
2. Clear Error Codes – Press the “Start/Stop” button repeatedly to clear displayed digits.
3. Firmware Update – Consult the Bosch service portal for the latest firmware; apply updates if available.

Addressing Vent and Airflow Issues

• Flush the Vent – Use a vent cleaning brush or a vacuum to remove all lint buildup.
• Check the Heat Exchanger – If accessible, clean the heat exchanger fins with a soft brush.
• Verify Back Door Seal – A damaged seal can lead to heat loss and cycle prolongation.

Electrical Inspection

• Fuse Check – Open the dryer’s fuse box; replace any blown fuses.
• Connector Tightness – Ensure all plugs are seated firmly.
• Motor Functionality – If the motor continues to run despite a clear load sensor, the motor control may be faulty.

When to Call a Professional

If after performing the above steps the dryer still fails to stop, the issue may involve the main control board or internal electronics. Attempting to disassemble these components without proper knowledge can lead to injury or void warranties. A licensed appliance technician can diagnose and replace complex parts safely.

Preventive Measures

• Regular Maintenance – Clean the vent and interior annually.
• Load Awareness – Avoid overloading; excessive fabric can jam the sensor.
• Temperature Monitoring – Keep an eye on cycle temperature readings.
• Service Checks – Schedule a Bosch-approved service check every two to three years.

Recap of Key Actions

• Clean or replace the load sensor.
• Test and replace the thermistor if needed.
• Ensure a clear vent and proper airflow.
• Check and secure all wiring and fuses.
• Reset or update the control board.

By systematically applying these diagnostic and corrective steps, most owners can resolve the “not stopping after load detection” problem on the Bosch WTG90 dryer. When in doubt, professional assistance ensures a safe and lasting fix.