While running the Garmin 530 I noticed the transponder's interrogator light (orange) flashing, but no transponder code appears; just blank black squares, no numerals.   The 430 does not have this problem nor does the default GPS. MS FSX is run in administrator mode, transponder knobs turned, not change.

 

Any thoughts?

 

sage

Ok, I'm not aware of any transponder light nor code in either the 430 or the 530 as the units are typically installed with a GTX-330 transponder system.

 

We don't provide any GTX-330 so can not discern why whatever unit your aircraft has does or doesn't function as expected.