MINTEMP triggered error (not a connection issue) (no replies)

Hi

I have a wired issue..

when i connect to Pronterface, i get reading of constant 0 C for bed/extruder temp.
the firmware is ok, all connections are ok and thermistors are ok.
the voltage on temp pins on the RAMPS 1.4 is 4.8-5V.
when i remove RAMPS and only connect the arduino, the temp readings are ~173 but are not constant, if i connect a thermistor to pin A13 and GND the temp reading reacts.
this happened after i tried to connect an LCD screen.
same reading on Marlin and Sprinter.

I'm losing my mind here... please help!