Thank you! I will update on the progress.
The box I got here: http://swechtrading.se/zencart/index.php?main_page=product_info&cPath=51&products_id=256
. I had to cut out the display myself and if you look closely you can see it is not perfect edges. But it's homemade so it doesn't have to be perfect
I really like the idea of morse code. I will defenetly look into that. The furnace already have lambda sensor controlled air intakes. Otherwise I would probably have done some tinkering there as well:). What I have been thinking about is to add a function to lower indoor temperature at night. The control system I have for that does not have that function.
I will look into putting the code online somewhere.
Thank you for the feedback.