When you do the autofeather check, make sure you have the condition levers in low idle. Ive never had to pull the levers momentarilly into beta in order to get a successful autofeather test.
Pretty common to be driving around the airport in high idle if your running the aircon. Make sure you pull the condition levers back to low idle when you do the test and it should work. If you close the left or right power lever and you can't get below 250ft/lbs of torque when in low idle, I'd say there is something seriously wrong with your rigging!
My 2 cents
Cheers
DB
