By Art MacCarley

WELLS or Duralast TU108 "Temp Switch" (it's really a thermistor, not a switch). It cost $8.99 USD retail and can be bought on-line, click here

  

The original part has a 7.22 mm probe bore and 10 mm straight thread. The replacement part has a 8.28 bore and a 1/8" NPT (US pipe) thread. Both have the same 22.5 mm probe length. Both have the same thermo-electronic characteristics. The replacement part can be modified using a small lathe or even a drill press and a file: Turn or file down the probe diameter by 1 mm. The wall is thick enough - see second photo with a test cut done using just a drill press and file. Take out most of the NPT thread depth, and undercut the area near the hex head just enough to clear the threads. Then rethread the threaded section with a 10x1 mm die. Smooth the terminal treads down until they behave like a male bullet connector. It takes a 1/2" SAE deep socket.