[svxistentialist]

Fully charged system and compressor working would seem to indicate possible electronic fault.

Is it possible you have a dry joint? Some wire that is giving a bad connection when the temp in the car is very high? Or possibly some circuit in the AC computer that only goes bad when the car interior is very hot?

My suggestion is you leave the car in the open, and let it bake. When it is fully hot inside, THEN run the AC diagnostic, and see if it comes up with a code. It might just indicate your problem.

In the case that it does not give you a code in these conditions, then rather than change in the complete system from your spares car, would it not make sense to just swap in the AC computer or control unit from the other car? This might be easier.

Joe