@namko - I only see a wired rain sensor in the current installation. Some municipalities require a rain sensor and/or freeze sensor to be installed on all irrigation systems. The way they’ll catch folks is if they see the system watering in a rain storm or when it is freezing. Rachio doesn’t require a rain/freeze sensor, but it can use it in combination with the weather data it receives. If the installation location has drastically different weather than the closest weather station, I might install a local rain sensor to catch the rain storm that the weather station didn’t.
The two wires on the right side of the top row are my guess as to the rain sensor wires.
Here’s the instructions (hint S1 and 24 VAC -) and don’t forget to tell the Rachio app that there is a rain sensor attached to S1:
FYI - the green and yellow wires on the top row won’t be used on the Rachio.