These special plugs make it easy to add a switch or gauge sender to your cooling system. The 1 inch OD fits into the branch of any of our Silicone Coolant Hose Tees (sold separately). The female NPT threads accept a temperature or pressure switch*, an electrical gauge sender, or even a petcock to bleed air out of the system. Black anodized aluminum for long life.
* Note: Grounding-type single-wire switches will require the addition of a grounding wire from the switch body to the vehicle chassis.
NPT nomenclature can be confusing! The nominal size refers to the inside diameter of the pipe, not the outside diameter of the threads. If you are not sure what size you need, check in our Threaded Plumbing Fitting Identification Guide.
NPT fittings can also cause concern because of the way they fit together. The threads are tapered to seal by an interference fit, which means that a properly-sized NPT fitting should never bottom out in the port. The male fitting should "jam" when screwed about halfway in. More information and torque recommendations can be found in our Guide to Using NPT Fittings.