Yes, I am surprised the FF made that mistake. I suspect that it was a case of form over function and easier maintenance. It is nice that the heaters, fans and thermocouples can all be changed easily without chasing long wires through the printer.

I actually made a different fix to mine. My Thermocouples still go to the wiring board but I connected thermocouple wire at the same screw as the thermocouple leads and ran those wires through the loom to the mother board. Because these connections are at the same temperature, there is almost no error introduced by having a connection in the thermocouple wiring.

That error in the data sheet refers to the temperature of the ADS1118. In our case when we print above 230 or so, the cold junction temperature approaches 40 (at the extruder wiring board) but the ADS1118 is closer to 30 depending on the ambient temperature. That means that the actual temperature that the extruder is maintaining is actually 10° higher than indicated.

The big benefit of fixing the thermocouple wiring is that you will KNOW what the REAL extruding temperature is and there is no chance of it running away and destroying your extruder or worse. As I said before, this risk is minimal if we stick to the suggested 230°. I think one reason FF may be slow to "permit" other filaments (nylon, PC, etc. is because of this risk.

Graham

With ABS the only real difference between 240 and 250 is that the 250 is usually too hot and you would not know it is 250.
Certainly when you get up near 250 the ABS carriage is also getting close to or above 50 even with the top off. With the top on, I think there is a real risk of warping it. I warped mine in the first week I had it before I knew about the thermocouples.

For higher temperatures, I think an aluminum carriage is the only way to go but even at 230/240 there is risk for long jobs in cooler ambient temperatures. The reason the risk increases in cooler temperatures is because the extruders still heat up but the ADS1118 will be much cooler this increasing the error.