I have a Prusa Mendle with a ramps 1.4 board. It's been printing fine for months, but last night the fan stared going full bore, even after a printer reset. Power cycle the power supply, when I turn it back on, the fan goes to full power immediatly. Sending M106 S0 or M107 does nothing. The power draw from the fan seems to keep my heated build plate from reaching temperature unless I just unplug the fan.
I'm looking for ideas as to what could be wrong. my assumption is that there's a short somewhere, but I'm not really that confident in where I should be looking.
Thanks