are you using your original under dash unit?
I used theirs and it is only piping through the firewall and needed hose line inside the cabin so I installed the valve there.

Also my motor in that controler failed after about 2 years. it doesn't have enough torque to turn the valve anymore.
I thought the valve was sticky and it turned out to be a common valve with a part chopped off, but after replacing it, it still wouldn't move.
haven't been able to figure out a better motor yet.