Question
The sprinkler system will not turn on and the box reads double XX.  I found one of the sprinkler heads needs replacement, I replaced it however, the system still will not work.  Please advise.

Answer
The sprinkler head will not affect the function of your controller, but its good to fix it.  Try removing the power from your controller for 3 minutes, including any battery backup that may be attached, and then reconnect the power.  Sometimes this helps to reset the controller.  Also make sure that the wiring connections are all secure where the wires to the valve are attached to the controller.