If your Thermador downdraft is not sucking or venting properly, there are a few potential reasons and steps you can take to fix the issue: 1. Check the Filters: The most common reason for poor suction in a downdraft is clogged or dirty filters. Remove the filters and clean them according to the manufacturer's instructions. In some cases, you may need to replace the filters if they are damaged or too dirty to be effectively cleaned. 2. Inspect the Venting System: Ensure that the venting system, including the ductwork and exhaust vent, is not blocked or obstructed. Remove any debris or obstructions that might be hindering proper airflow. 3. Verify the Blower Motor: Check the blower motor for proper operation. If the motor is malfunctioning or not running at the correct speed, it can lead to reduced suction. If the motor is faulty, it may need to be repaired or replaced. 4. Adjust the Speed Settings: Some downdrafts have adjustable speed settings. Make sure the downdraft is set to the appropriate speed for the cooking task. Higher speed settings should be used for more demanding cooking situations. 5. Ensure Proper Installation: Double-check that the downdraft was installed correctly and is aligned properly with the cooktop or range. Improper installation can affect its performance. 6. Professional Assistance: If the above steps do not resolve the issue, it's best to seek assistance from a professional appliance repair technician. They have the expertise and tools to diagnose and fix complex downdraft ventilation problems, ensuring optimal suction and ventilation performance. Keep in mind that downdraft ventilation may not be as effective as overhead range hoods, especially for heavy-duty cooking. If you find that the suction is still insufficient after trying the above steps, consider consulting with a ventilation specialist to explore other ventilation options that better suit your cooking needs.