Quote Originally Posted by HarleyBalls View Post
Sounds like you might have a rheostat/dimmer not a thermostat, a dimmer just regulates the current being sent to the UTH, a thermostat should do as described and monitor the temp to what you put the setpoint at and turn the UTH off and on as necessary. A dimmer style stays exactly where you set it and you will see fluctuations due to room temp changes.
Oooh, maybe that's my problem... it is called, Zilla Reptile Terrarium Heat & Habitat Lighting Temp. Controller, 500W, it doesn't say thermostat...does this sound like one?