The most common reason for non-activation on a Hunter rain sensor is the sensor itself has not encountered enough rain fall. Go out to the rain sensor and manually activate the sensor switch by pressing the Quick Response Spindle (labeled in the image below). Do you hear it click? If so, the rainfall on the sensor hasn’t reached the deactivation threshold. (If you know that your rainfall has exceeded your rain sensor activation setting, you may want to consider moving the sensor to a different location.)
The rain sensor switch is in the “BYPASS” or “OFF” position. To fix this, slide the switch into the “ACTIVE” position.
During installation of the rain sensor, the terminal jumper was NOT removed. To fix this, remove the terminal jumper located on the sensor (SEN) terminal screws.
Note: Hunter rain sensor's will only overide systems when the system is activated in a Manual All Stations mode. Manual Single Station will not allow for operation to be interupted.