New thermistor isolation, how? We are trying to repair an Ultimaker Original+. One problem is a missing resistor isolation. The Ultimaker Original+ prints with up to 260 Degree Celcius.

Which kind of isolation products are suitable to resist the heat and are fitting on the thin wires of the thermistor?
The most common choice for insulating thermistors is glass fiber sleeving. It tolerates very high temperatures, and is commonly rated for up to 600&nbsp;&deg;C.

Teflon is also used but has a rather low upper limit on its working temperature; it shouldn't be used at temperatures exceeding 260&nbsp;&deg;C - which rules it out for your purpose.