Rob in answer I checked today and there is only one OAT sensor and to confirm there is only one set of Pitot/Static connections and logically these are attached to the EFIS display which is for the Pilot and it is this unit I used to make the OAT calibration changes on.

When I made the initial changes the temperature in the hangar was steady at 10 degs C and yes I did momentarily touch the sensor to see if the OAT value on the EFIS display would rise.

Today on power up the OAT value displayed was 14 degs C however the ambient temperature in the hangar was showing as 12 degs C as measured on a mercury thermometer.

Given that it is probably never going to be possible to get the EFIS OAT value to match the measured OAT temperature I guess a 2 degs C differential is going to acceptable assuming that the error is linear so it is not worth trying to get the OAT calibration to be more accurate.

Can I ask again why is there the need for a second calibration point and what will be the impact of making no changes to the settings that are already entered for that calibration point?

After confirming that there were no Pitot/Static connections onto the second EFIS display then after it had powered up I checked the Instrument Calibration settings for the OAT and saw that the Instrument OFF/ON value was at OFF from this can I assume that there will be no interaction between this unit and the master unit in respect of the other OAT calibration values?