DS18B20 problem - 127°C

[dudo02]

wilxt - its for thermoelectric valve on radiator which is 230V.
pat - you are maybe right. I cant replace the cable. I will try diode on relay and if doesnt help I try to use it transistor for relay switching. Another possibility is try to use SSR relays.

[dudo02]

Try use flyback diode parallel to relay!

This is solution. Thanks so match for help to everyone.