nmrdude

There is another reason A/T will not arm besides engine generators being off.. The alt target in pref is set higher than the aircraft can reach at current weight. If this happens and you are flying, vnav should be OK and should mange speed target but you will need to manually move throttle up to ~n1 of 96% or so to have reasonable power for proper climb rate. Once established A/T might arm if alt target on dash dial is OK. In any case once at stable flight on climb profile more or less go to pref and lower alt target to something reachable at weight and set mcp dial on dash to match.