I've recently upgraded my Original Ultimaker (bought in 2012) with this dual-fan mod from NeatherBot:
Everything went great, except I can't seem to run the fans at anything less than 240/255. At full speed, it seems a little excessive and is quite noisy.
I'm running the latest Marlin firmware, and the latest version of CURA. I've tested the fan speeds by just manually sending commands through CURA.
These are the fans:
Any help would be greatly appreciated.