thermistor temperature shows 0 degrees

Hi guys,
After struggling several months with my reprap to make it work, I have a problem after three days of printing.. :/ everything was working like a charm, I used PLA, and today I tried with ABS, so I augmented temperature choosing ABS presets in Pronterface, it worked for a few minutes, I melted ABS, but after a while it didn't work anymore, nor the thermistor can warm, neither the information of temperature of the thermistor in Pronterface, it says 0 degrees.. So, the problem is localised around the thermistor, the bed is able to warm and it sends the information of temperature in pronterface.
If anybody knows..., welcome
manu

mmm... I just made a new test: I interverted the connections of bed thermistor and hotend thermistor on the RAMPS, to see what happens in Pronterface..>The hotend was able to heat but the thermistor gave me only the temperature of my room..?? After that the ABS who was stuck around the hotend melted and two parts felt. I joined a picture, ... It's my thermistor that is broken, right?

That is a broken thermistor.

okay, thanks! already shopping