Just found some comments in my Lionel notes by Jon Zahornacky regarding the placement of the thermistor to the heating resistor; found them somewhere in the forum (have been looking for them again for hours but no luck) and put the comments in my notes:
Jon Zahornacky, aka SanaFeFan (smoke unit engineer for Lionel, retired) said that the smoke units were engineered for the factory block of wick to work with the heat resistor, a thermistor located 1.6mm from the heating resistor and with the wick block a certain distance and density to the heating resistor. You cannot buy the factory block of wick. So, it is critical that you locate the replacement wick and its density and thickness and depth as close as possible to the original factory block and not block the fan air holes.
1.6mm converts to 0.0629921 inches which converts to 1.009/16ths.
Correction to the description to Jon's career: Jon was more than a smoke unit engineer; he was a great engineer and inventor and held many patents for his work; happy retirement Jon!!
