Yes it's accurate when return temperature value, I measure tip temerature with other thermocouple on multimeter... It's does no have to be 150C exactly but around it... sometimes it's works correctly for short time, and on higher temps. I added readError code to sketch, and I am getting 2 & 4 witch is shot to gnd and short to vcc, I don't think it's fault sensor in heat element, as i sad before I remove it from circuit when it start problems and measure resistance and it's not open.... Yet when it start bugging I remove it and connect one from multimeter its reading fine.... So my guess is cold joints maybe, I could not solder it on wires so i crimp it, and probalby some more passive components... I forgot to mention i am using 0.1uF ceramic cap on TC terminals and 2 ferrite coild one on each end of TC.
Edit: found problem. So I have a full circuit there... I am driving Triac (with AC) it's opto isolated... Funny thing I have a transformer hooked inside ATX PSU enclosure with switch to turn it on.... Moment i put power cable from mains, transformer is off but thermal readings start to bug.... What is it? If i unplug cable everything works fine. Transformer is off could it be Earth wire it's ESD....?
EDIT2: Yes definitely! It's Earth wire. Solved. Thank you.