I have 2 chest freezers...1 that I use as a kegerator and 1 that I use for fermenting. I use the Johnson digital thermostat controls for each and they work fantastic. My only complaint is that I have a little trouble keeping it warm enough in the winter, which is when I usually resort to fermenting in my pantry. Your broken thermostat should not be an issue if you can plug it in and it still turns on, but I'm no repairman! Cheers!
Life is too short to drink crappy beer@
Kegged: Super Hoppy Red Ale, IPA
Bottle: Barleywine, Belgian Chocolate Red
Fermenting: India Brown, Pale Ale