Important Service Bulletin 10.1 Series EFIS Displays Serial #3000-3140

GRT Avionics Service Bulletin – 10.1 Series EFIS Mod A, March 28, 2022

This service bulletin is for the field repair of 10.1 series EFIS displays. This repair is an authorized customer installed modification. It requires approximately 10 minutes to complete. Contact GRT Avionics to receive modification parts free of charge. If you do not feel you have the ability to perform this modification, fill out a Service Request Form available on our website and send the EFIS to GRT Avionics. GRT Avionics will modify the EFIS and return the EFIS to the customer free of charge (ground shipping only).


It has come to our attention that some 10.1 series displays may have intermittent side row button functions.

Affected Units

All Horizon 10.1 and Sport 10.1 EFIS models with serial numbers between 3000 and 3140. Check your EFIS ID plate. If it has a hole thru the ID plate in the “Mods” section, where the “A” was or if the “A” is scribed out, your EFIS has already been modified and no further action is necessary.

Repair action

The modification requires the installation of two insulating shims between the rear cover and main circuit board. This modification is known as “Mod A”.

10.1 Series EFIS Mod A Instructions