K2 Plus Nozzle not heating as expected Issues

[actuallyhello]

Hi, this is my first post here.

I’ve been using my K2 Plus for a few months now and hadn’t had any issues until about 3 weeks ago. I started getting occasional “Nozzle not heating as expected” failures, then they started happening more often. I can rarely get a print to work now.

Printing in ABS, nozzle @ 240, bed @ 100, chamber @ 60

I’ve tried nozzle PID calibration a number of times - I thought a new heater in my printing room was causing issues, but have worked out that is probably not the issue.

I’ve tried checking, tightening plug connections on the thermistor and the heater, they seem nice and tight. No damage to the circuit board either.

I’ve tried using previous firmware (1.1.2.10) in case it was a software issue but it has very similar problems to the latest firmware (1.1.3.13).

The failures seem to happen after the chamber heater tries to increase temperature. I’ve managed to get some prints to not fail by turning the chamber heating off.

Since this is an issue that has suddenly appeared and is getting worse, I am guessing that it is a hardware failure somewhere, but I’d like to nail it down before trying replacement parts. The printer is still quite new, so its a bit disappointing that I’m having problems so early on. Any help would be appreciated.

Below are some temp graphs of some of the failed prints if that helps:

[actuallyhello]

I downloaded the log files and have some fault codes:

{
“list”:[
{
“dateTime”:“2025-10-10 19:21:11”,
“time”:1760084471,
“code”:2564,
“error”:4,
“msg”:“Heater extruder not heating at expected rate”,
“value”:“”,
“isProcessed”:false
},
{
“dateTime”:“2025-10-06 20:30:30”,
“time”:1759743030,
“code”:2060,
“error”:2,
“msg”:“Heater extruder not heating at expected rate”,
“value”:“”,
“isProcessed”:true
},
{
“dateTime”:“2025-10-06 20:27:56”,
“time”:1759742876,
“code”:2564,
“error”:4,
“msg”:“Heater extruder not heating at expected rate”,
“value”:“”,
“isProcessed”:true
},
{
“dateTime”:“2025-10-06 20:12:12”,
“time”:1759741932,
“code”:2564,
“error”:4,
“msg”:“Heater extruder not heating at expected rate”,
“value”:“”,
“isProcessed”:true
},
{
“dateTime”:“2025-10-06 19:39:54”,
“time”:1759739994,
“code”:2564,
“error”:4,
“msg”:“Heater extruder not heating at expected rate”,
“value”:“”,
“isProcessed”:true
},
{
“dateTime”:“2025-10-06 19:01:11”,
“time”:1759737671,
“code”:2564,
“error”:4,
“msg”:“Heater extruder not heating at expected rate”,
“value”:“”,
“isProcessed”:true
},
{
“dateTime”:“2025-10-06 18:33:29”,
“time”:1759736009,
“code”:2564,
“error”:4,
“msg”:“Heater extruder not heating at expected rate”,
“value”:“”,
“isProcessed”:true
},

[actuallyhello]

There was also some nozzle temp “wiggling” without the print failing:

[rdtsc]

@actuallyhello

nozzle @ 240

Hi, your hot-end likely needs to be rebuilt.

Reason why, is “standard” heatsink grease is only good for 200 C or so, long-term. Running a nozzle at 240, 250 or higher causes it to dry out and stop working fairly quickly, leading to heating issues.

Rebuilt mine with boron-nitride heatsink paste, which is good for higher temperatures but is harder to work with and requires a lengthy low-temp drying period. Note, the heater cylinder is retained by a ring which is reverse-threaded (careful!) and held fast with a tiny lockscrew.

Once you change the heatsink grease, you’ll want to perform a nozzle heater recalibration. Think there is a Klipper macro to do it automatically. Had some difficulty with that too, and required more than a few passes to calibrate fully.

[actuallyhello]

Thanks for the suggestion, I’ll look into the hot end grease.

It still seems odd to me that the hot end would be at fault when the print tends to fail on chamber heating, but succeeds when no chamber heating is used.

But at this point I have to try everything. Having a printer that is unreliable is really frustrating.

[actuallyhello]

Just thinking about your reasoning about the heat sink paste being the issue.

If the heat sink paste has gone to crap, more heat is needed to get the nozzle to and hold temperature, so when the chamber heater kicks in, the power supply might not have enough power since the nozzle is using more than it should.

I’ve ordered some new heat sink paste and will update this topic after rebuilding the nozzle and doing some testing.

[rdtsc]

I knew the paste was an issue because as soon as the silicone sock was removed, the ceramic heater seemed loose and could be wiggled easily a tiny bit, which it should not do with good heatsinking. Note that the hot-end also needs a little grease, on the top copper ring after the heat-break section - you’ll understand once it is apart (should already have grease on it, likely dried out and crusty.)

[Mrburns]

Give thought to this - the two holding screws. Bad contact will realise bad heating

WARNING - K2 Hot end nozzle assembly can come loose. CM2784

Glad it helped I would urge others to check their nozzles. Especially those having Z height issues. You never know, so its worth a check just to eliminate the possibility.

[actuallyhello]

I just checked all the screws around the hotend and couldn’t find any that were loose.

I’m still waiting on new heat paste to arrive, will update this thread in the next few days.

[actuallyhello]

Cheers, I appreciate the extra info.

[actuallyhello]

UPDATE

Took hotend off the printer, dismantled it, removed all the previous heat paste, put new heat paste on and reassembled.

Tested using same settings as before that was causing failures, printed two small prints before it failed again with same error.

Performed a PID calibration since I forgot to do it after rebuild.

Tested again with small print and same settings. Had a bit of a hotend temperture wiggle, but 6min print finished.

Print 50min successful.

Print 50min successful.

Print 50min successful.

Print failed before starting to print – nozzle not heating as expected.

Replaced hotend with a new one.

Performed PID calibration.

Print 40min successful.

Print 40min successful.

Print 2hour successful.

More testing will see if problem is solved, but I’m cautiously optimistic that a new hotend has fixed my problem.

If the hotend replacement has fixed my problem, that’s great and all, but having a failed hotend on a AU$2.2k printer within a couple of months is not inspiring confidence.

[Martin_Prent]

I get the hottend error when my petg need to dry. I can get the print started when its not to wet i set the temp from 250 to 255 to get the temperature more stable. Maybe you can something with my experience have printed more then 1600 hours with the k2.

[actuallyhello]

Bloody hell, 1600 hours Impressive!

My filament is in CFS holders, so I’d like to think that the filament is dry and ready for printing.

[Martin_Prent]

Its like the Devil play with it. Last couple of days printing abs get the same problem. It was the thermal pasta it was powder when i removed the nozzle. Have renewed it and that problem solved. Now i got the retraction problems again have replaced for the third time the 4 way hub under the cfs. the hub begins to eat the fillament and then the tubes tears. The last 4way hub had i installed some extra washers under the spring it held out couple of hours think 150. I did that because i got retraction errors. Dont know what the problem is anymore for me the hub can print like 500 hours without big problems then it start al again.