Decided to bend it nearer the heatsink and add goo.
At switch on , at about 13V you cannot hear the fan at all. At 24V, after
heating the thermistor, it is
just about noticeable with absolutely no ambient noise around. So little
point to being variable let alone respond to air/board temp.
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on