Avidyne IFD550 Pilot's Manual page 393

Unit Overtemp -
Check Cooling
<component> will show the name of the component(s) that
have exceeded temperature limits.
One or more of the internal components has exceeded
80°C. Contact the Avidyne Service Center or a dealer for
service – consider adding a source of cooling and/or
improving air flow in and around the IFD.
Xpdr Fault
The remote transponder is reporting a fault other than loss
of ADS-B GPS position. Contact the Avidyne Service Center
if this persists across power cycles.
Unit Overtemp: <component>
Transponder Fault
IFD500 Series Pilot Guide
General 7-15