From my experience it only asks "new/old" when it doesn't know.... When you first attach an atty (with both at the same room temperature) you sets that reading as new. From then on it only asks if it needs to. Try this and see what you get:
Using your current setup.... fire the atty until you reach the temp limit message.... remove the atty and fire the device....reattach the atty with the coil that has not cooled down and when asked "new/old" select old and you should be good to go (note resistance),,,,repeat and when asked select new and see how different the resistance reading is (remember the coil was not at the same temperature as the device)....thus if the device sometimes does not ask "new/old" it thinks you have the same atty..
maybe this explains....