Flew leg #1 in my RV7A yesterday and everything worked fine..the 430w with no messages, all functions working on the D-180 and the AP 74 hooked up and performing all functions just fine. Parked the plane (in the hot sun) for 3 hours. Returned to the plane for the trip back home. After startup and turning on the avionics master the 430w booted up normally, all satellites received and then displayed the message as shown in the photo. I was unable to set the altimeter in the D-180 as the function switch was inoperative for altimeter setting. Took off and headed home (vfr of course). In flight the autopilot would engage and the altitude hold worked fine. But I had no heading input because the heading function was not working and the GPSS steering function would not track in the Nav mode. ATC confirmed receiving my ADSB altitude info. So, I guess my question is what could be possible reasons the 430w would all of a sudden lose a connection as per the message and where do I need to look to start troubleshooting what is missing in the system. Thanks