The fast idle on mine has always been a bit intermittent
Just had a quick look at it and can't make much sense.
I measure about 750mv on pin 47 but it doesn't change with fan & lights.
Measured the voltage on the fast idle valve connector (the 2 pin one if I've got it right) and I have got a constant 13.5v regardless of electrical load. The valve is working as the revs drop when I unplug it.
Did you manage to find if its driven through a relay, and if so where it is?