Thanks for the spreadsheet, great stuff!
I'm hoping the "From/To Select monitor" pins will give me the ability to read/write values (get data, and send commands). This will probably be the quickest/simplest way, although it has the over head of figuring out the 'select monitor' commands without having an original 'subaru select monitor' to eaves drop on.
Another option could be building a custom HVAC controller board which connects directly to the motors, sensor, etc, and skips using the original SVX HVAC computer board. But that maybe more work. There are some existing projects for car HVAC controllers:
https://hackaday.io/project/159707-hvac-car-control
https://github.com/jgmuchiri/arduino...limate-control
Those could help speed things up a little.
Thanks!
Ian.