THX for the details on testing the RPM- huge help. Mine were running over 3K. Thermador double oven (SEC model 2005). I have been receiving F64 codes and they were getting worse and worse. I flipped the breaker to the oven, stacked cinder blocks and wood in front of the oven, and slide it out onto blocks. I then pulled off the back and top to access the fans. I used a shopvac, toothbrush, 100 (seemingly) Q-Tips, and a acetone. I gently scrubbed the fan blades until shiny. The amount of junk that came off was incredible- cups of junk. I put everything back and did a fan test- 2400. Oven has been running for over an hour at 400. I searched everywhere and this is the only place with accurate info- THANK YOU!