Give Rich a call at Reptile Basics. Describe exactly what is happening. He can tell you if it is a thermostat problem. I have somewhere around 10 of the VE's in my reptile room. I had one that would not reset properly during a power outage (one of the earliest models). Rich replaced it promptly. Other than that, I've found the VE's to be very good thermostats. I use the VE100's as back ups on all of my racks.