Which sensor? There is a sensor on the INLET with 3 wires (2 red, 1 black) and there is another sensor on the side of the OUTLET. There are only 2 wires on the outlet sensor with spade connectors.

By the way, I just checked this and now the other LED light is on (between OVERTEMP and SENSOR). Before, only the LED between SENSOR and FAIL was lit. Do you know what each ones of these mean?

Thanks