i think i may have found the answer, i was having a problem with the ATO overrunning once it had reached the sensor and couldn't get my head round the problem for love nor money.....it would seem however that on a totally separate screen from the ATO screen, there is a little drop down box where you can assign the sensor for ATO main sensor. i'll give it a little test in the morning :) you would have thought they would have put the drop down for the ATO on the fricken ATO screen lol go figure