Sag Manual - Water Valve Mod

[T350 Al]

I've been using Graham's ever-useful Sag Manual to sort out hot air in the cabin issues to pretty good effect. I noticed in the modifications section at the back that he's used a Ford water valve to stop the hot water circulating within the heater matrix to stop all hot air flowing to the vents.

I'm now looking to do this mod on my T350 but can't seem to find the 'Water Valve' wiring he's referring to. In the manual it says that it should be tucked away under Throttle Body 2/3.

Can anyone give any help in finding this or advise if it's even present on the T350 at all?

Thanks in advance!