Umm... if you make your fans spin very fast with a blower there's two issues.
First, if you make them spin faster than designed you'll kill the lubrication of the bearings by excess heat. And then of course the bearings will die because you've burned the lubricant off.
Second, if you make any kind of an electric motor spin by other means than electricity, the motor turns into a power generator pushing electricity backwards into the system. Again, excessive speed may produce more power than your system can handle. I bet you haven't unplugged the fans during the cleaning process...
[Edit] Skuzzy the Lightning Finger was faster again