johnson temp controller reading way too high

i use a Johnson temperature controller for a ceramic heat bulb to warm my wort during the winter. i keep the bulb and wort in a freezer thats acts solely as a fermentation chamber (the freezer does not work, so all i have is a heat source in a sealed container basically.)

on my current beer, my controller has been acting up, i turn the controller on with the set point to 67 degrees. i come back after a few hours and the controller is reading 119 degrees! the heat lamp attached to the controller has cut off thankfully and the actual temp of the beer (according to a temperature strip on the carboy) is 60 degrees.

so whats happening, i think, is that the probe is broken because it reads a completely high and wrong temperature; causing the heat lamp to shut off, leaving no heat at all so the actual beer temperature is too low. anyone had this problem? do i need a new controller?

How close to the heat source is the probe and are you measuring fermenter temp or ambient? If the probe is on the carboy and insulated, the lamp will likely get pretty warm depending onthe temp swing set on the unit. It may be broken, but you would only have to replace the probe, not the whole unit. It only takes a few minutes.

did you try testing the controller against a known thermometer? like your one you use for brewing? try heating up a cup of water, and use one as a ice bath and see if you are getting the same numbers on both instruments in the different baths. Porter Pounder has some good advice there too. measure the side of your fermenter and insulate the probe with a piece of Styrofoam or something. I used to use that technique before i got a thermowell (that is the Best option) Bulbs can get pretty hot and with the insulation in the freezer i would not be surprised
if it was getting that hot in there.

thanks for the info, i just compared the probe temp to my brewing thermometer and the probe temperature gradually just keeps going up, like a degree every 30 seconds. so i guess i will just replace the probe. hopefully that does the trick.

Thanks again