1 1/4 x 3/8 NPT SENSOR TEE WITH GROUND LEAD ALLOWS YOU TO SPLICE INTO YOUR INLET HOSE AND INSERT A TEMP SENSOR **SENSOR NOT INCLUDED** The OPTIONAL Z18346 is a temperature switch that closes at a preset heat. When closed the switch is completing a path to ground. The Northern 3/8NPT TEE is typically insulated from the vehicle ground because it is mounted in between two rubber hoses. To avoid sending stray current into the coolant a grounding strap must be provided.