Why not wifi?
 

We replaced ours with a B-hyve (Amazon). Took some work to set up - they'll help if you need - but it works great!

They don't exactly work as you think. The Rachio controller runs a soil model and makes watering decisions on a daily basis. While the forecast in our area is part of the calculation, the actual observed precipitation is the primary driver of whether it irrigates, for how long, and which zones are irrigated, on each day. I installed the Rachio when the original Hunter died. Installation and setup was about 90 minutes or so; ideally you will measure the inches per hour for each zone and that will take a bit of time. One of the other benefits is that you can turn individual zones on and off with your smart phone, which makes adjusting sprinkler heads convenient. When you travel, you should leave your wireless router on because the controller will not function correctly without a Wi-Fi connection. Mine is located in the low voltage panel in my garage and has no problem picking up the Wi-Fi signal from across the house.

My last 3 homes I put in the b-hyve Orbit smart controller. I’ve replaced over a dozen of my friends old worthless controllers with the b-hyve controller. I think they cost around $50-$70 for a 4 station. If you can use a screwdriver, it will take you 5 minutes to swap controllers and mount the unit in the network box. It’s pretty easy to configure it, probably 15-30 minutes to get that done. Now running it in SMART mode, it will run the stations when needed and it will vary the amount of time each station will run based on the criteria you put in and from the data it receives from the weather station you assign to it.
I bought my own personal weather station so my b-hyve get very accurate weather data

Hunter controller
 

I have one.

I have one for sale. Works fine. I just wanted a WIFI capable one

My irrigation water usage costs about $7 per month. So, I think a high tech watering controller is overkill.

I did the same!

I didn't buy one to attempt to save money, although I may very well be doing so. My Hunter died and I needed to replace it. The convenience of being able to control zones from my smart phone, while adjusting sprinkler heads, was well worth the incremental cost over a minimal controller. When the HP 35 came out, I guess some people thought that was overkill when compared to a slide ruler ;-)

https://upload.wikimedia.org/wikiped...35_Red_Dot.jpg

Slide rule - Wikipedia

I am very interested in installing a b-hyve to replace my hunter controller. I had it done up in New York and it wasn’t that easy. I would love ask for your advice and or help.

As far as the weather forecasting being inaccurate, I agree. The Rachio lets you select weather from local weather stations which makes it pretty reliable.

Even if my rain sensor worked perfectly, I may save a dollar or two per month at best.

You can get a Hunter controller at Burry's Ace Hardware. I've replaced two of them, one due to lightning, and it is very simple to do. Make a note or diagram of where each wire goes to the existing controller and reconnect them in the same fashion to the new one. As I recall, the cost was less than $100.

I still have the original controller. I have an on/off switch for the rain sensor but I leave it on. If it works great we won’t water if it rains and if it doesn’t work then the sprinklers turn on. Not sure what you gain by disconnecting the wires. I’m interested to know.

The only way to disable the solar sync function is to disconnect both wires. This disables both the solar sync and the rain sensor. You cannot disable the solar sync without disabling the rain sensor as well. The solar sync function is worthless and it takes control of your watering times, which is not acceptable. That is why I disconnected both wires.

Maybe in your case but I'm saving a significant amount of money on water since using the Rachio. More than paid for itself in a short amount of time. Everyone's situation is different.