are you hooking your indicator bulb into the heating coil circuit ? ... if so you need a bulb rated for the maximum voltage of that circuit. the bulb determines it's own wattage depending on the voltage to it. ( the bulb has internal resistance built in so that it doesn't run away and blow up )
most simple heater coils are at 115 volts, so a house lamp bulb would work. ( a 15 watt night light bulb would be least obnoxious ) . maybe your ebay test bulb was for 12 volt car circuits ?? ...
or .. i bot a lyman lead thermometer and used it twice until i just learned when my pot was real hot ... maybe the smell ( g ) .
hoping this helps, simple is always better.