Cast Head to Aluminum Head Coolant Senser

Have a question I changed the heads on my SBC from stock cast heads to Aluminum heads. I used the Coolant sensor switch that was in the cast heads and installed it in the Aluminum heads. The sensor switch is used to run my electric fans. How that the sensor is in the Aluminum heads the fans turn on at about 140 were as before they would kick on at 180. Is there a different coolant switch I should be using ? Have any recommendations?

Material shouldn't make a difference. I'd look at grounds. Make sure the fan and engine have a common ground along with the relay that's used. Could be that during the swap some wires got moved? Also, you shouldn't use teflon tape on the sensor. If you feel you need something, use the paste instead.

I used Teflon thread sealer. I will take the sensor out and remove the sealer. Thanks for the reply.