Can anyone tell me what this is? It's in my engine by up by the battery. It has two wires coming off of it. Seems like a sensor. A friend of mine unplugged it and doesnt remember where it came from. It's from an S4 TII.

 

I am not 100%, but looks like the coolant sensor from the radiator.

 

Yeah, it's the thermoswitch from the bottom of the radiator.

 

Apparently I don't need it then since I have an aftermarket radiator and haven't had any issues thus far.

 

you probably have an s5 aftermarket or some custom/universal radiator. the sensor helps with the aws but you are correct, its not needed

 

looks like your middle finger..... thats not too polite =(