*Sigh*

I know how transponders work. No you don't get constantly pinged. Yes the plane is supposed to flash as it's being tagged by radar. No that's not what I'm talking about.

I meant to say text on lower left. Do you want a photo? It displays text: SBY/GND/ON/ALT corresponding to switch position. Mine works for maybe 20 minutes, then displays dashes where the text was. Same issue with a different hesd unit and transponder in my plane today. Starting to think it's the wiring harness, more specifically the data line connecting the head unit on the panel and the box in the back. Running dual batteries, both lithium....power supply shouldn't be a factor. Antenna shouldn't make a difference to the display. Still troubleshooting. Next step is to try another harness, and check mine for breaks and bad solders.

Jordan