I purchased a MES 40 (model 20070710) in October 2010 and am very happy with it. However, I have found that the temperature reading on the MES display consistently shows 20-30 degrees higher than the temperature shown on my Taylor 1470N digital thermometer. (I checked the accuracy of the Taylor using the boiling water method and found that it was within a few degrees of 212). To compensate for the MES display error, I set the temperature on the MES control unit 20-30 degrees higher than my desired temperature. This works OK for things I want to smoke at 225-250 (ribs, butts, etc) but it does limit me from smoking at higher actual temperatures (e.g., 275 degrees for chicken, etc.). I moved the Taylor probe around a bit inside the MES box and still found the disparity. I am thinking that either one of the sensors inside the MES is at fault or the control unit on the top of the MES is at fault. There are two sensers on the back panel of my MES 40. One is at the top left (sensor #1) and the other is in the middle right (sensor #2). I have read that the #1 sensor is called a "limit sensor" and the #2 is called a "temperature sensor". While I get the general idea as to what these sensor may do, I don't know how to test them or if they can be a likely culprit. In short, these are my questions: - If one of these sensors can cause a display error, which one is it most likely to be? - Can the sensors be bench tested using a multimeter, and if so, are there any specs (e.g., ohms/voltage at a specific termperature) for testing them? - Is it more likely that the control unit is at fault, and if so can it be tested using a multimeter or any other way? For cars, appliances and such I don't generally like to throw parts at a problem without first diagnosing a failed part. Perhaps it is not feasable to do this on the MES and that guessing is more practical. If so, I would appreciate your "guesses" before I order any sensors from Masterbuilt and remove the back panel to replace them (which would be a pain). Thanks in advance for any responses.