You do not have a problem with flaps. These only control the output. There is not a mixing door to adjust temperatures (as used in some Fords).

Neither the sun sensor nor the emissions sensor (your codes) are the problem. Either you have a leaking duovalve, a low refrigerant charge, or a restriction in the refrigerant circuit.

To test the duovalve, carefully pinch off the heater hose going from the duovalve to the engine and repeat the test.

To test for low refrigerant charge or a restriction, evacuate the system and charge it fully by weight. If the system now functions correctly, you have a leak. If the left side is still warm, you have a restriction.