This is a (Optional) Pump Ready thermal switch. This thermal Pump Ready switch, is to be attached to the side plate of the AX-65 Pump next to the over temperature thermal switch. This optional thermal switch can be connected to a light to show when the pump is at operating temperature. It is normally open and closes when the pump reaches operating temperature. The switch is set to close at 170ºF (operating temperature). See graphic for installation/location on the pump.