I'd assumed they were temparature driven. Read that the VIII's 260 model IC spray is programmed to activate at the lower temp of 23 degree's C with the WRC Tech upgrade kit... to make it more usable in the cold UK climate.
Given the VIII 260 is pretty similar to a VII I'd think they both operate that way. So something above 23 degree's and it'll come on if set to auto, I wanna say 27 degrees but I may be imagining that.