Anyone know how its installed? I was thinking about ordering one but I'm not sure if its cable-driven to open the heater valve. Any info would be great before ordering one.

 

If you're talking about the "Auto Aircon" one, it won't open the heater valve. The cars that came with those had an electric motor that opened the valve.

However, it will plug in, light up and "work".. You just won't be able to control the temp without extra parts.