posting this for information only
customer reported aircon not working so did a few checks and found pressures down so did a regas but as expected it still did not work. further checks discovered if we powered the compressor the clutch came in and pipes instantly colder but the fan did not run so further checks were required. the vehicle returned today for the repairs and we checked all the fan wireing only to find a purple wire badly corroded where it enters the control module behind the fan. the unit was only available from ford and expensive so i stripped some of the casing back and soldered a new wire in and reasealed it. after reassembly all was well.
i dont think this will be an isolated case so hope this helps somebody in the future