The AutoMeter pyrometers are calibrated to within + or – 2% accuracy at full scale reading. What this means, is that we purposely make sure that the hotter the probe is, the more accurate the gauge is. Therefore it is not uncommon for the outside temperature to be 70 degrees, and the gauge is showing you something different, such as 32 degrees, or even something a little over 100 degrees. This is not a cause for concern. After all, when it comes to this gauge, we want to make sure that it is giving you proper readings at hotter temperatures, where it matters the most. Generally, the gauge has come into full calibration by 600 degrees.
If you decide that you would like to check the accuracy of your gauge, and you do not have access to a calibrated thermocouple simulator, you may simply remove both probe wires off of the back of the gauge (this applies to models with threaded terminals for the probe wires), then turn the power on while both probe wires are removed. You should see a reading that lands anywhere between 0 and 100 degrees. This range, for this test is an acceptable range.