I was trying to install my FC thermosensor today, but since the plastic on the harness and coolant temp sensor were brittle, it broke off the coolant housing. To make matters worse, the harness has part of the sensor still stuck in it, seems to have melted together.

Now I am wondering if even need to put this temp sensor back in? What readings does it give the ECU?

 

The FC Thermoswitch change does not interface with the ECU; it is used to set the cooling fans to the next higher speed.

The Water Thermosensor does interface with the ECU and is required for engine controls.

I would not eliminate either.