Originally Posted by Bry195

look up the temperature scale of a 10k (NTC) thermistor. its a resistor that changes resistance to ground as temperature rises. Its also inside the motor. you dont have the problems that ir sensors have (emmisivity). measure the resistance between the ground pin and the thermistor pin on the efra connector on the motor. its typically 10-15 degrees hotter than temperature on the outside of the can. Different colors will change the accuracy of IR temp. the distance from the measurement also needs a compensation factor.

not every motor mfg puts the thermistor in but all the motors I buy do.

if you just really want a good temp gun then you can do 1 of two things. measure something the color of the can at a known temperature and move the gun to the distance that gets the right temperature and write down the amount its off. then always use that error amount and distance. they are usually repeatable just not accurate.