A Class PCB codes

Following on from yesterday I'm trying to figure out how to read the codes on the pcb, once I start cyclying through S1 etc I see whole numbers and letters, but when the system is sitting at normal the display is showing fragmented symbols, could be numbers or letters, what should it display at "normal" and does this indicate a general Board error?

Thanks

When normal.
Should show bars
Which mean different things.
Like pump on
Boiler on
Etc
Mike