Yesterday, I opened the controller box (Rainbird ESP 4MI) to see what time it was and I found the alarm led on. All zones work fine in manual mode and in test mode. Nothing on the display panel indicating a problem. I'm suspecting a problem with the rain sensor - a Hunter Rain Click. The alarm light went off when I flipped the sensor switch to "bypass". Alarm comes back on when I put the switch back on "active" The Hunter sensor is wired to the two "sens" terminals in the rainbird. Any ideas what would trip the alarm light? It had rained earlier in the day and the sensor may have still been wet. The irrigation system was not scheduled to run until today.