Auto Adapt to my understanding is only available if you have a Mitsubishi thermostat. It increases or decreases the flow temperature depending on the measured room temperature versus the required room temperature. So it's not on / off.
I've heard mixed opinions on it from people.

The issue with the external temperature reading is a common one. We've seen differences between the reading and the actual of 15C at moments, which of course throws your weather compensation completely off. Best is to have the sensor on the north face of your building but even then there are errors.

Posted by: @richard24738

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Does the Auto Adapt also take into account the weather compensation settings in some way?

If it does then I may have an issue in that the external temperature reading is extremely high when the sun is out and that would presumably confuse the ecodan algorithm.

My understanding is that it uses the WC settings as a starting point.  Exactly what it does from there and whether it 'times out' any measured modifications and constantly refers back to the WC settings has not been published as far as I know.

External temperature sensor should, as @hcas says, be on a north wall or otherwise shaded at all times from direct sunlight (note that 'north' walls can get quite a lot of sun in summer, particularly if they aren't actually facing due north).  The idea is to measure the air temperature only.  

Agree with @jamespa on both!

We're now using weather station data instead of the external temperature sensor. More accurate! 

@hcas That's interesting. There must be some sort of algorithm or AI going on. Maybe similar to what Homely does?

How do you use weather station data on a Mitsubishi Ecodan?

@richard24738 Auto Adapt is quite simple in nature, nowhere close to what Homely does. 

You can't use weather station data on the "out the box" Ecodan. We wrote our own control algorithms from the ground up. 

@hcas I guess something like Homely would be the answer although for some reason Ecodans are not supported.

Has anyone actualy moved the Ecodan Outside Temperature Thermostat? It seems to be on a very short wire.

Today the Outside reading was 19c versus an actual at the side of the house in the shade of 15c. 

@richard24738 I think some heat pump controllers allow you (probably only in installer mode though) to adjust the external temperature probe to correct such problems - might be worth checking yours. Regards, Toodles.

Posted by: @richard24738

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@hcas I guess something like Homely would be the answer although for some reason Ecodans are not supported.

Has anyone actualy moved the Ecodan Outside Temperature Thermostat? It seems to be on a very short wire.

Today the Outside reading was 19c versus an actual at the side of the house in the shade of 15c. 

Can the wire be extended.  If its just a thermistor, which is fairly likely, it will have a pretty high resistance so extending it with some ordinary cable wont affect it.  Thats what I plan to do with the DHW tank sensor for my (planned) Vaillant, and all the installers I have spoken to believe it will work.

@toodles Thanks. The problem is that the Outside temperature gain only occurs when it's sunny. Normally it's ok.

I think the heat on the wall behind the pump reflects back on to the pump.

Anyway, we will see what Mitsubishi say. Maybe it''s just a case of moving the heat pump a bit further away from the back wall.

@richard24738 Tricky one that as I imagine you don’t wish to construct a sunshade for the brickwork behind the pump. Ours gets the sun on the brickwork but has not created a noticeable problem (though the temperature probe is in shadow behind the pump) - ours is some 30 cm. away from said wall. Regards, Toodles.

@toodles My gap is 39 although there is plenty of room in front of the ecodan if I wanted to move it forward a bit and maybe move the plant pot a bit further away.

I have attached a photo of the location. It was a sunny day!