A little thought on this, prompted by observations sitting in my car for a while today with the engine idling after not having been started for over a week.
(I wasn't specifically there to check the fan, but given recent problems decided to take note of its behaviour)
The main thing I noticed (recalled really) is that in "Auto" the HVAC does almost nothing for quite a while.
It's a boring autumn day, maybe 14/15C outside (but no sun) and the system is set to 21C both sides.
So, it's checking temperatures all round, including the coolant reaching it and initially pretty much decides to do nothing, fan speed on 1 bar only.
If I play with temperatures, absolutely nothing happens if I set it higher, because (obviously) there's no heat source. Set much lower and it starts to blow cold and increase the fan speed.
All very logical. 
And without a powered auxiliary coolant pump there's probably not much, if any, hot water getting to the HVAC unit. It's probably all being recirculated to warm the engine up faster.
Of course, after a few minutes when the temperature gauge started to move, it all sprang into life.
So, my conclusions (at last!). It seems to me that MOST of the symptoms described here are down to normal/intelligent HVAC behaviour, probably exacerbated by inaccurate/faulty temperature sensors (but which ones) and the lack of an ACP motor.
Though low flow through the heater matrix if it's partially blocked won't help of course.
Incidentally my valve unit looks the same as the one you have installed (picture repeated), not like the one purchased. I can't actually see any motor or where it is.
Maybe under the air intake?
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2003 D2 FL S8. Irish Green Pearl/Beige. Solar sunroof, auto-dim mirrors, electric rear seat functions, ski hatch retrofit; extended leather. Aftermarket DVB-T, reversing camera and full XCarlink (Bluetooth etc.).
2016 Volvo V40 T5 Cross Country (4WD) with ALL the toys including adaptive cruise etc. etc. Osmium Grey with Blonde/Charcoal leather interior. Polestar performance "optimisation".  (A much rarer model than a D2 S8 by the way!) Oh, and a brand new engine at just under 30,000 miles on the factory one! 
Finally: gone, but not forgotten.....
1998 D2 PF S8. AgateGrey/Platinum. Every option (I think) except electric rear seats, tiptronic steering wheel, ski hatch, towbar & dimming door mirrors.
e.g. Cruise control, NavPlus/TV, Bose, GSM, Xenons, Solar roof, Parking sensors, Alcantara/leather everywhere of course. (internal dimming mirror added later)
1998 (very early) Ford Focus 1.8 Zetec; ABS/TCS, Heated screen/mirrors, Aircon, Auto-dim mirror, Leather, Trip computer, Cruise control, OEM Ford SatNav with CD changer.
And before that a lot of Rover 800s, a few oddities, a lovely Triumph Dolomite 1850HL with Overdrive and way back in my schooldays an Austin Seven aka Mini 850!
Last edited by HPsauce; 5th November 2018 at 02:27 PM.
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