My kiln did not shut off for my last bisque firing last Sunday. I knew it wasn't getting hot enough. Couldn't see the glow between the lid and the base. After wishful thinking shut it down after 17 hours. Checking with a meter found it was the top switch. Looked like it had a little nest in it. Got a new one from Cress in 2 days, installed it and today bisque fired again..off in 7 hours. I hurried it a bit since everything was almost 04 but had no idea what cone.
Last glaze firing the kiln sitter cone broke and shut it down early. Everything was unfired. Orton said to tug a bit on the cone before using. Then if they are weak or cracked they will break and you won't risk an underfire. I refired and everything turned out fine. I had about 10 in the box pull apart. I think I'm due a few good firings in a row now.
Hope all goes well. It could be the damp ware. I am very conservative and glaze fire very slowly 13-15hours.