Originally posted here by Tim_axe
You won't be able to determine the RPMs of the fan through the 4-pin "Molex" adapter. If you look at your CPU fan, it has a special 3 pin plug. Only these kinds of fans can have their RPMs monitored.

As for adjusting the speed of the fan, !mitationRust got it right. A rheostat / fan controller can lower the voltage being applied to the fan and make it spin slower with the reduced power. I doubt the RPMs could be monitored through the Molex plug, but I could be wrong...

A controller such as this can allow you to adjust the fan speed...but it can't tell you the fan speed: http://www.newegg.com/Product/Produc...82E16813999504
hehe, let me know if you want any free **** from the egg like T-shits or any "I'd rather be pimpn' my PC license plate frames.....I'm good buddies with a few of the egg's sales reps. The T-shirts are gay too, they're orange. 'I've confronted the egg on price gouging before. They have great refurb stuff and specials too.........but I hate paying their tax........that's why I use zipzoomfly (google gear) with free second day shipping no tax.

That's a good question; I've never really given a damn about my RPM's only Dba.

As for the fans, I think they need what's called a tach wire or some type of sophisticated circuitry that monitors the tach pulses or something of that nature........ read up on this dank stuff here www.controlres.com This is where the telecommunications people are at and a lot of their stuff uses still air and not fans, not even their PSU's, so when they recommend a fan in a system, it's definitely needed, and when it goes out they need to know ASP!

http://www.controlres.com/alarms.htm

I've already ordered these just to try them out, I’m betting they're loud as furk but my Sunbeam rheostats will take care of those.

$2 25mm you know I'm gonna give that a try!
http://www.voyeurmods.com/index.php?...=7&prevstart=0

I recommend Sunbeam because they're the workhorses of the industry when it comes to pc rheostats IMHO.