My thermistors arrived earlier than I expected. So, I tested the two that arrived before rebuilding the extruder. These components also appeared to test open. Three bad components? No way. Then I noticed my ohm meter was set at the high range. Ok, expensive lesson learned here. After switching to the lower range, they tested fine. Even the "bad" one.
So, I re-wrapped the extruder assembly with one of the new thermistors. (Hey, might as well use good looking components) As an experiment, I also added a "K" type digital thermometer probe to the other side of the extruder block. This is from a Harbor Freight digital thermometer (cen-tech 92242) to calibrate or at least be a real-time check of the extruder assembly's temperature.
Post construction note: I'm really glad I installed a separate thermocouple thermometer. Although the software control panel can show temperature when in the control panel window, I can't display that window when I do a build. By having a separate digital readout, it's possible to "see" what the bot is doing. This is handy to establish if the bot is simply waiting to get up to temperature or if there is a problem.
