Hi guys.

I’m trying to figure out where my temperature problems on my Dremel 3d20 Idea Builder are coming from. When heated it is showing a too high temperature, e.g. when preheat to 220C I measure around 160 on the heater block with my external measuring device. Of course not much is coming out of the nozzle when the printer thinks it is at 220 but in reality it is at about 160C.
Idling in room temperature the printer starts at beeing off only 1 degree but after some minutes it is off by 5C from what my measuring device shows. So the printer does not show any error messages which I read in other posts that it would do in case of a thermocouple problem. So this might be a motherboard problem? So should I go for a new motherboard (which would be risky because I would have to buy a mainboard ver2.2 from flashforge whereas my dremel is ver1.2). Or can it be a heating element problem? Or is it the thermocouple nevertheless?

Do the extruder and bed read a similar temp when it has been off for several hours so it is at room temp?
I think you will find trying to get a temp from the outside of the hot block is not going to be very accurate due to the heat loss through the block, nozzle and barrel/cool section.

Will it extrude anything at that temp?

It does not extrude anything. The dremel does not have a heated bed so I can only compare printer readout temp with my temperature measuring device. I stick it’s metal probe in one of the two thermocouple holes in the heater block. The other hole has the thermocouple inserted obviously. So the thermocouple and the measuring probe are at the same place relative to the heating element so I would assume they should show roughly the same temperature but it’s 220 to 160, so a difference of 60C. As mentioned in a previous post at room temperature the diff is only 1-5 degrees. Does that indicate a faulty thermocouple? Would like to know beforehande because it is 20 euros a new one

That is kind of a tough one.
Maybe you can find a specification for the thermos so you can test is to see if it may be faulty.
I am not really familiar with the printer. Is there a dual extruder model? Maybe the board has inputs for a second extruder you could possibly use to test the thermos from?

You’re right, the board has a second input for a thermo. But the socket is missing. To test it I would have to solder a JST PH socket to the board which would be an ok task for me. But I am sceptical because I assume it would also need firmware modifications which I’m not capapble of and the dremel printer is not so much open sourced as far as I know. In short I think the printer would not know by itself that it now should use mainboard connector T2 to measure hot end temperature.
The thermocouple has like 3 ohm resistance by the way. so basically continuity.