Temperature sensor issue

Hello,
I have a issue very annoying… when i switch on my Zim, right fan (cooler nozzle) is activated.
Octoprint shows that my right heater block (tool 0) at 67°C. I verified connectors, everything seems good.
When I set temperature to 180°C, it seems working.
I removed right heater block and Octoprint still shows 67°C insteed of “off”

I don’t know what to do…
what to check

ps : left heater block (tool 1) is good. It is at 28°C

check the connections of thermistor or the thermistor could be faulty

I tried to connect an other heater block but it didn’t fix the issue.
I disconnected right heater but printer always shows 68C instead of “off”

–> saying Temp was 68°C is pretty strange, due a short circuit would be 0°C, and a broken wire (open circuit) would be 250°C.

Test:
start with a cold heater.

watch the temperature graph. Normally both of them (left and right) should display your room temperature.

set the temperature to… let´s say 70°C.

If you can see the temperature graph going up immediately degree by degree, your problem might be some “temperature offset” or “correction factor” in the software. Could be fixed by reflashing your Pi and your Zimboard.

If your graph stays on 68°C for a while and then pops up to 70° (or maybe even overheats some), your problem seems to be a faulty thermistor.

To be sure about that, let your zim cool down, remove both heaters and reconnect them on the opposite connector (just let them hang loose, as they are normally not interchangable). If your Problem is now on the other head, it´s the temperature sensor.
BUT: If you still have the behaviour on the same heater (it didn´t switch sides with the heaters), it may be a problem with the small circuit board at the head (some kind of partially shorted circuit or something).

first image : all heaters are disconnected

both heaters are connected (I removed the bed)

right temperature set to 80C

both set to 80C
when I touch heater, heat is not the same between both. Left one (T1) is warmer than right one (T0)

Okay…
so your zimboard gets wrong informations from the printhead. It´s been pretty good that you also had both heaters disconnected (I assume that you also had the temp sensors disconnected).

So, please also disconnect the ribbon cable that goes to the printhead from the zimboard. If the problem persists, the location of the problem is in the zimboard. If the problem seems to be gone, you´ll have to check the cable and the Circuit board at the backside of the Printhead.

Let´s hope that it´s the cable.

I disconnected the head ribbon… I guess i’m not lucky…

T_T I guess it will be very difficult to fix if it is zimboard

Yes, that´s f**ked up…
But it could be worse… Maybe you can contact @BDub or @jpod regarding a value in the firmware to control the right cooler fan, wich is powered on at 60°C. If you would raise it´s value from 60°C to 70°C, the only drawback would be a wrong graph. The fan would be powered off, and you could fully use your zim.

I think value to change is in temperature.cpp

void CheckTemperatureToActivateFan()
{
if ((degHotend(0)> 60 ) || (degHotend(1)> 60 ))
{
digitalWrite(FAN_v2, HIGH);
}
if ((degHotend(0)< 55 ) && (degHotend(1)< 55 ))
{
digitalWrite(FAN_v2, LOW);
}
}

I will try to change value… I need to figure out how to manage offset temperature for my right heater because I think if I set for example 80C, heater is not really at 80C.

easiest way for the offset is the offset function in octoprint. Although it is not the most elegant option…

custom firmware to 75C for right nozzle works.
But offset temperature in octoprint doesn’t work, I tried to offset until 80C but nothing change.

At least my Zim is not out of service… i hope, i will try to print something.

Hi…as per my knowledge If you can see the temperature graph going up immediately degree by degree, your problem might be some “temperature offset” or “correction factor” in the software. Could be fixed by reflashing your Pi and your Zimboard. If your graph stays on 68°C for a while and then pops up to 70°, your problem seems to be a faulty thermistor.To be sure about that, let your zim cool down, remove both heaters
and reconnect them on the opposite connector. If your Problem is now on the other head, it´s the temperature sensor.

circuit board assembly

please also disconnect the ribbon cable that goes to the printhead from the zimboard.

PCBA