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Extruder preheat error

#17202 (XL)

Relevant for

XL
12 comments
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What happened?

The message "Extruder preheat error: Check the heater and thermistor wiring for potential damage" is shown when the printer is unable to heat up the nozzle more than 2 ºC for 20 seconds. The printer starts a safety feature, which instantly kills the heating process and displays the message on the screen. The printer then waits for the user to inspect all parts and if needed fix the issue.

Error name: Hotend preheat error

Error code: #17202

How to fix it?

Most often, this error happens due to wiring damage or connection issue on the hotend heater cable. Less often, it might be caused by the hotend thermistor wiring and connection. 

A visual inspection

Before breaking out the multimeter you should check the Dwarf board, where the thermistor and heater reside, to ensure that no wires have broken off, or are disconnected. 

Before you start, make sure:

  • the filament is unloaded from the extruder
  • the printer is turned OFF and unplugged from electricity
  • the hotend and the heatbed are cooled down to ambient temperature
Because we will handle tools and work with the extruder high above the heatbed, it is necessary to protect it.

Place an empty Prusament cardboard box approximately to the front center part of the heated. Move the X-axis all the way to the front side of the printer, and move the extruder approximately to the center of the X-axis.

Open the dwarf-cover-door to access the Dwarf board.

Check that all the connectors are secure in their sockets, according to the picture below. Focus on the thermistor and heater cables. Though unlikely, rough shipping or handling could have shaken the heater or thermistor cables loose. 

Checking the resistance

The table below describes the correct resistance for each part, as well as what scale you should set your meter to. The hotend thermistor is rated to be 100 kΩ at 25 °C. To be realistic, with a varying temperature between 20 °C and 30 °C, you can expect a wider range of readings (~80-125 kΩ).

There can be micro-fractures in the cable, breaking the connections only at certain positions. Therefore, try to move the cable a bit while doing the measurement and see if the value changes drastically.

Part
Resistance
Multimeter scale

Hotend thermistor 

[80 kΩ - 125 kΩ]

200kΩ

Hotend heater

[12.3 Ω - 15.1 Ω]

200Ω

The part should be cold (room temperature) and unplugged when measuring the resistance!
 

8 comments

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Barlichn
My Tool Changer on #4 spot will not heat up. When it gets to 25c the printer reboots and comes to an orange screen with error 17202. I have checked all the wiring that the Tech took me through for #3 two days before and that did not resolve the issue with #4. I swapped Tool Changer 4 over to spot 2 and Tool Changer 2 over to spot 4. Tool Changer 2 works on spot 4 of the Splitter board. However, Tool Changer 4 on Spot 2 of the splitter board does the same thing on that spot; reboots the printer and comes back with error 17202. This shows that the splitter board works, and the draft board on the Tool Changer does not work. Need the draft board on the tool changer replaced. I have only had the printer just shy of a month. I was in the middle of a long print when #3 and #4 failed.
Barlichn
I am receiving this message on #3. I have visually checked the wiring and see nothing wrong. I have been printing for a few weeks now and today this one is having issues. I do not have equipment to test the resistance nor have the knowledge of same.
Barlichn
Tech Support was able to get this one up and running by having me swap the tool changer power cables between spot 2 and 3.
sliverbaer
How do you unload the filament if the thermal runaway keeps triggering?
suprchunk
Printer crashes when preheating from PrusaConnect. This article doesn't describe the fix for this bug.
 
IronEnol
I get the same problem
GAD
The alarm screen does not indicate which toolhead is having the problem.
Marina Curzi - Official Prusa CS

The error only happens on the tool that is selected at the moment. If you have any trouble finding it, contact out technical support.