if you turn the lights off in the room and have the IR lamp on, you shouild see a red spot light without having to look at the filament. if a red light isnt coming out then yes, it sounds broke to me, although it shouldnt work at all if the filament is broke. i also agree about the gauge type thermometers, even though i use one myself, i figured out how to keep the needle steady. only problem with them is that if a light is shining on them, that'll increase the temp on the gauge, making you think the temp is higher than it might be, as the light will give it a higher surface temp, aswell as the temp in your tank. my leo has light all the time so i dont use an ordinary white light, and sliding the UTH in and out helps my temp, and use the red bulb to boost the temp a little bit if it looks a bit under/over. and yes a digi therm would be best.