Vagreys,
When I was looking on Craigslist in my area I was seeing the same price range from $100 to $200 for used ones. When I did the search I just put in "wine" in the appliance section search and this unit popped up. I thought at first it must have been a typo, I just got lucky that no one else beat me to it, probably because at that price it must be a piece of junk. This makes up for all the times I didn't get a good deal, we have all been there.
Saucisson,
Sounds like a thermocouple problem also. These things have two heatsinks on each thermocouple. One very large one on the hot side of the thermocouple to draw away the heat with a fan blowing over it and another smaller one on the wine cooler side with a fan pulling cool air into the cooler.
The problem with most any electronic device is overheating, if these units are put in a space without proper ventilation then the thermocouple will overheat and give out. Another problem is that when people replace these components they don't apply thermal grease, thermal grease is very important because it makes a very good conductor to draw heat away from the thermocouple and to the heat sink where it can be dissipated.
That was the problem with this unit I picked up. The fans and heatsinks were full of dust and dirt and when I removed the thermocouples the thermal grease had dried out and just crumbled. The reason I mention the dust and dirt is because a heatsink, usually made out of aluminum will dissipate heat very well except when it is covered in dust and then they are not as efficient.
Anyway if you could post some more symptoms maybe I could point you in the right direction. If the fans are working and the digital display, if it has one, is working then the circuit card assembly is probably okay.