So I am modifying a system to use a lower rpm fan than it came with. This is the original fan.... http://partner.delta-corp.com/Products/FANUploads/Specification/QFR1212GHE-SP01(REV01).pdf The wiring says... Red = + Black = - Blue = STO Yellow = PWM The blue wire looks like a RPM reading off the fan. My thought was to use https://www.amazon.com/DROK-Frequen...17714814&sr=8-1&keywords=pwm+signal+generator And set it to the frequency I want the system to think its running? I thought I could get this to work, but it doesn't seem to recognize the PWM output from the DROK as a rpm. I have +12 going to the vin+, 0V going to the vin-, and the PWM out going to where the blue wire of the fan was. Do you guys have any advice on how to achieve what I need. I see a lot of references to using a 555 timer to create this, but I thought I could use the PWM siginal generator to have a visual representation of the frequency. Anyhow I am open to any suggestions / info.. Thanks!