Are there not AP test Level 1 and 2 checks you can do on the ground? Either with engines running or hydraulics hooked up?
Error codes are usually generated and can at least point in right direction for troubleshooting.
Will usually display as 1Exx 2Exx for respective system.
The xx number will narrow it down though you will need Honeywell manual to refer. I.e, Bell MM not much help.
We had similar issue with 4 axis system on ILS GA 412EP. Turned out to be a accelerometer. Not saying that's your issue but run the BIT level 1 and 2 checks and see what codes you get.
I am assuming 3 axis has the same BIT modes.
Good luck.
Last edited by Salusa; 15th October 2019 at 10:08.
Reason: Update