550 Aircon issue from Feb17 2018

I had an issue with lack of intermediate settings on the fan speed,at first it was thought that a faulty ECU ( Ferrari part number 65200900 ) was the cause,this is shown in the manual as item 4 on the picture of the heating/cooling unit ( behind the aircon control panel ),using details from previous posts I removed the side panel on the Left hand side of the centre console ,air bag, glove box etc to get access to the ECU which was replaced with no effect ,so I had to find a source of variable resistance elsewhere.The panel on the Right side of the centre console was then removed and a fitting was found which performs this function (Ferrari part number 64280200 ),it was faulty and replaced ,now the aircon/heater works perfectly (it may be item 8 Page I 11 drawing I 0065 in the manual and called a Solenoid valve adjuster).My Maranello 550 is Right hand drive.
The aircon unit is made by Diavia in Italy and Ferrari P/N 65200900 is also marked 875240 - 462003500 Modulo ECU 12 V 132085 and Ferrari P/N 64280200 is marked Diavia 133000/2 12V CEU/5 , made by Btron "A" and made in Italy