Bad Thermistor in Hotend? - Hardware, firmware and software help

RE: Bad Thermistor in Hotend?

Neverdie156 — Sat, 06 Jun 2026 06:10:20 +0000

I solved my problem — I replaced the LoveBoard and everything works as it should.

RE: Bad Thermistor in Hotend?

Neverdie156 — Sun, 10 May 2026 05:19:35 +0000

I have the exact same problem. After replacing the thermistor, it's still the same. With the thermistor connected, it's 160°C, but without it, it's 40°C (room temperature is 20°C).

RE: Bad Thermistor in Hotend?

JoanTabb — Tue, 05 May 2026 00:09:14 +0000

Good news!

best wishes.
Joan

RE: Bad Thermistor in Hotend?

Job — Mon, 04 May 2026 19:32:27 +0000

Per your suggestion I unplugged the thermistor and the temp reading dropped to 0°C so yeah it looks thankfully it look like a bad thermistor and not a controller issue.

RE: Bad Thermistor in Hotend?

JoanTabb — Mon, 04 May 2026 15:53:43 +0000

sorry I initially read the value as 22C not 22oc

220C suggests that the thermistor circuit is low resistance, worthwhile changing the thermistor,
220C is not low enough resistance for a shortcircuit.
If you unplug the thermistor, the display temperature should go below 15C and give you a mintemp error... if it doesn't, suspect a controller issue.

Good luck

Joan

RE: Bad Thermistor in Hotend?

Job — Mon, 04 May 2026 15:24:41 +0000

I'm pretty sure the heater isn't cutting on because the hotend temperature reading is erroneously >220°C at room temperature.

RE: Bad Thermistor in Hotend?

JoanTabb — Thu, 30 Apr 2026 20:45:40 +0000

Shine a hot hair drier on the hot end see if the temperature changes, if it does, the chances are your thermistor is good,

when you instruct the hot end to heat, does the hot end temperature change? If not the heater is probably disconnected from the socket or faulty...
it could be a broken wire on the heater itself or in the wiring bundle between the controller and the buddyboard, or faulty connectors... or the heater block may be faulty..... Worst case, the Mosfet on the controller board may be faulty...

regards Joan

Bad Thermistor in Hotend?

Job — Thu, 30 Apr 2026 20:13:16 +0000

When I start up my MK4 the live temperature reading for the hot end reads around 22o °C, while the hot end is room temperature and it stays room temp when I attempt to preheat the system for printing with PETG.

Is this a bad thermistor that needs to be replaced or is there some other trouble shooting I can attempt? This is pre-built system less than year old.