i have an AEB engine and i noticed i have both the blue and black temperature sensors right next to eachother, why would that be?

also my temp guage was going all over the place rendemly between 70-105 inaccuratly with both connected, i disconnected the black one and the car wouldnt start with just the blue one, i disconnected the blue one and wallah the temperature readings are steady and working fine

my question is why do i need two of them connected? would it be safe to drive with the blue one of the hook?

 

by the way ive already replaced the blue one and that didnt help at all