Hi,
I have an AF-4500EE with an internal back-up battery, a few months ago I turned power on to the system before engine start and saw nothing except the large red attention getting light, driven from pin 14 of the EFIS main cable, light up after a few seconds. This was the 2nd flight of the day, on the 1st flight it started normally. As I was in a hurry I started the engine, where upon the box started up and behaved normally. The problem did not re-occur for some while, but now is happening more often. Usually starting the engine brings the screen into life. On one occasion it has not. I left the aeroplane for a while with the master switch on, the screen still did not come one when power was cycled, but did when the engine started. This is a single screen system, so I need it to be reliable!

Can anyone suggest a what is happening and how to fix it?

Peter