Nate F Dover , MA July 29, 2016 Appliance: Thermador Cook "N" Vent Downdraft System CVS36RS Thermador Range Hood Cvs36rs: Downdraft wouldn't stop going up and down and finally got stuck in up position. How to replace Vent Switch. Replaced the up/down switch and it works perfectly 1 People found this story helpful Do-It-Yourself Rating: Repair Time Estimate: 15-30 minutes