Ok a couple of questions. Is your thermo probe taped to the bottom of tank over the UTH? Or is it actually taped to the UTH? Also do you have a Temperature gun or just the Acurite thermometer you using to read the temps? It can be one of 2 things: 1) your probe is not in the optimal spot which is throwing off your temps or 2) the thermometer you are using is inacurate. I use herpstates on all my cages and the #1 reason I find when my temps are off is due to the prob getting moved and not setting the correct temp. If your not using a temp gun I would highly reccomend one as they are the most acurate. I have used the acurites as well and for the most part they are very good but they can go out of wack and be incorrect as well...