hi there, i seem to be having a problem with my rain sensor. it rained Saturday and i checked my system to see if it turned off since it was supposed to come on the next day and sure enough it still showed it to be coming on the next day! so i was a bit concerned but not much, it had happened when they first installed the system but we checked everything and it seemed and was fine. so i pour a bit of water on the sensor and look at the display, it shows "system off, sensor". that is good. the next day i go see if it has reset to its 3 day cycle and sure enough it only showed two days left. since it was going to rain again that day (and it did) i figured OK, the system is going to turn off and reset to the three day cycle but of course it did not. it did not even turn off and showed 1 day left. so i pour water on it again and this morning the display shows: the flashing sprinkler head sign but it also says sensor off. how do i go about checking what is wrong?