Insignia G09 - cabin heater system

[FenrirXIII]

Hi all! Please help with following: when I`m setting air system to AUTO - no matter what temperature is set - it blows with cold AIR.

As well, when AC is Off, I have to set warm temperature to 23 and above to get warm air but then it becomes really hot.

So, the question is - how to make that temperature regulator actually work? I.e. what to check / clean / replace? I`ve tried looking from the side of glove box - it`s a mess of everything, so a bit of schematics or advice highly appreciated.

Thank you in advance