get one from carter. while your waiting for it to arrive heat up a pan ful of water and drop a thermometer in the water along with the bulb and slowly raise the temp of the water to 180-200 to see if the bulb somewhat matches your thermometer. while your at it, drop your thermostat in too and observe its operation in regards of temp with the bulb and thermometer from closed to fully open. it will keep you from guessing later.