Thanks Chuck.. The year of the car is an '84. It is the forward most sensor on the head, with the double wire connector going to it. The next one back I believe tells the computer where the engine's temp is to adjust fuel mixture, as when I pull that single wire off the engine runs rough, slows down but blows black smoke, like a rich mix. The last one back I think is the aux fan control. ******** AZ lists the switch as the thermo time switch, and has a hefty price of 103.00.