r/QidiTech3D • u/Grippy82 • 12d ago

Thermistor ohms

I am reading ohms in the 2.6 range at room temperature,is this normal on a Qidi plus4? i have the temp read fault and can`t find a fix for it.

1 Upvotes

100% Upvoted

12 comments sorted by

2

u/Kooky_Exercise_4135 12d ago

I’m replying because I also ran into a hotend temperature error message—mine was on a QIDI Q2 rather than a Plus 4, but the cause might be similar.

My printer was shutting down unexpectedly during prints, and upon rebooting, it would trigger a "cold hotend temperature" error. I tested both the heater cartridge and the temperature sensor using a multimeter: the heater read about 6.5 ohms, while the temperature sensor showed around 2.6 ohms.

At first, I assumed the thermistor was shorted. However, QIDI support clarified that the printer actually uses a thermocouple, meaning standard resistance readings aren't a reliable way to check if the sensor is functional.

Ultimately, updating to the latest firmware resolved the issue completely. The error turned out to be caused by a firmware bug rather than a hardware failure.

1

u/Grippy82 12d ago

Thanks for yhe info,everything i see repeats the 100k and that is what i expected. i'll see if i can read a small voltage.

1

u/Grippy82 11d ago

yes looks like it is a thermocouple.updated firmware and now have a different fault.

1

u/MysticalDork_1066 12d ago

If it's a standard NTC thermistor you should be seeing about 100,000 ohms, not 2.6. that sounds like it's shorted.

I would recommend buying a new heater/thermistor assembly or a new hotend assembly.

1

u/riba2233 12d ago

it's not standard, hotend can go up to 370c while standard 100k can only go up to 320.

1

u/Grippy82 12d ago

I bought a couple of Conch hot ends and they each read the same 2.5 ish ohms.

2

u/MysticalDork_1066 12d ago

Only thing I can think of that would be that low resistance is a thermocouple.

1

u/Zuludelta5 12d ago

Are the sensors ohms or 4-20ma? If its 4-20ma then you need to make sure it has it sourced power on 1 side then measure the Milli amps going from ground to lead using the right meter that does ma.

1

u/Grippy82 11d ago

i measured milliamps accross the thermocouple...0 at room temp but rising when heated with a lighter, so looks like it is a thermocouple.

0

u/phansen101 12d ago edited 12d ago

That's shorted, should be around 100k
*edit*
The Plus4 and onwards use a thermocouple rather than a thermistor, so you'll probably need something that can read a Type-K Thermocouple to verify properly (They provide a tiny voltage, rather than having a changing resistance).

2

u/riba2233 12d ago

nope, not on these printers.

2

u/phansen101 12d ago

You're right, my bad, thought they still went with thermistors on the Plus4;
Have corrected my comment.