I have a sensor on top of my thermostat housing. I know about the temp sending unit for the gauge. I know about the temp sensor for the ecu. But what is this single wire that goes to a what looks like another temp sender. It only has one wire. Also, this wire appears to have been hot at one time. I recently got the car and do not know what the history is besides rode hard and put up wet. I am new and any help would be appreciated.

 

What year is the car?

If I'm thinking of the same wire it is for another temp sensor that was only on cars equipped with an automatic transmission.

 

It's the temp switch for the auxiliary electric fan in front of the AC condesnsor. The switch turns the fan on if coolant temp gets up to 207degF. The fan also runs when the AC is turned on.

 

^ Exactly. Fan thermostat switch.

 

If you have an aux fan, and the key is ON , and you pull that green/black wire off the temp switch, the aux fan should come on.