Detecting if a furnace is lit

So I have a display condition for an 'image' in a certain blocks GUI that checks for a lit blast furnace one block above.

Heres the procedure I use:

If I remove the part that checks for if its lit, the procedure works fine. 
So it must be a problem with how im checking if its lit??

Anyway if any of yall can tell me how to get this working that'd be great!