I agree with a couple of psters on here. If the probe is up on the glass 2 inches above the substrate then that is ambient temp not real uth temp. You need to put the probe in the substrate right over the uth. If you can't get a thermostat then get a rheostat at least. If you are using both lights and uth then you need to turn off the light. Poor little guy is probably boiling. Also don't cover the whole top with plexiglass. You need air circulation also. I have saran wrap with a piece of foil between covering 2/3 of the top. I also have 3 sides insulated with a blanket and a towel over part of the top and half the front. I can't get a plug in thermostat here in town so I need to order one. I do have a rheostat set on low and my girl is switching between the cool and warm side hides. It is a matter of experimenting to find what level to set the rheostat though. My probe from an acurite indoor outdoor temp humidity guage is right over the uth and the body is on the cool side. Temps and humidity is right on. You can get one for about $12 at walmart. You don't need to buy an expensive reptile one when these work exactly the same, and are cheaper.