I turned up my system and the battery in the rain sensor was dead. I replaced it and got everything working. Now the sensor will not sync. I do not see any light on the sensor. Looks like there is a liquid inside the sensor where the light is located. Is there supposed to be any type of liquid inside the sensor or is mine full of water?
I would recommend contacting Rain Birds website. The instruction manual is there, along with FAQs. As far as any liquid, perhaps it is water. I sold their products while working for a distributor and never recall hearing that question. I empathize with your frustration. Normally that product is pretty trouble free.