im swaping blocks from a b16a to a b18c1, the b16 has a 2 wire bullet type sensor. i was told that it is a coolant fan sensor switch. i thought that was on my b16 head below the vtec switch. their is a similar sensor on the thermostat housing which i was told was the new coolant fan swith on the b18 that i needed to rewire the 2 wire switch too. if someone can back this up or sort me out thatd be great!

 

if its right underneath the intake manifold then its the knock sensor