That's what happened to mine. I bought 3 med zoomed UTH last august. All 3 of them were on their own t-stats, about 3 weeks ago all of them stopped working, I thought it was weird and took apart my cages (I have stacking showcase cages). It turns out all 3 of them had burn holes all over them. I'm lucky it didn't start a fire. I immediately replaced all of it with flexwatt.