Fan Speed Controller (hydrofarm) broken after 1 day, 2 seperate occasions!?! Wtf?

hey all, ive had 2 hydrofarm fan speed controllers now burn out on me. they work for about a day regulating the fan speed. then the next day i go in, the fan only runs on full blast and the controller "off" function wont work. its like the controller circuitry permanently defaulted to full on, and im wondering what might cause this? its happened in 2 seperate units, both hydrofarms, both failed within 1-2 days..... any ideas would be appreciated, my mind is at a loss.

I have had 2 Hydrofarm 6 inch inline duct fans burn out in the last month. Sorry about your control.

You might try a heavy duty ceiling fan speed control from hardware store...