IF statement returning false with no data

Forgive me for my trivial question, I'm sure the answer is simple, but I've been looking at spreadsheets and VBA for the whole week and my brain is fried.

I am working on an elongated IF statement that produces different outputs depending on the start of a part number e.g. 3XXXXXXX = Software, 4XXXXXXX = Hardware.

The problem I am having is that the formula outputs 'FALSE' when a part number is yet to be given to the row.

=IF(B2>0,IF(LEFT(D2,1)="1","Assembly",IF(LEFT(D2,1)="2","Sub-Assembly",IF(LEFT(D2,1)="3","Software",IF(LEFT(D2,1)="4","Hardware",IF(LEFT(D2,1)="5","Chemical",IF(LEFT(D2,1)="6","Spare",IF(LEFT(D2,1)="7","Spare",IF(LEFT(D2,1)="8","Document",IF(LEFT(D2,1)="9","Misc",""))))))))))

Please let me know if you can spot where I am going wrong!

Thanks, Dan