Prusa error 13526 (Loadcell Measure Failed) appears on the MK4 and is reported as #26526 on the MK4S, #21526 on the MK3.9, #27526 on the MK3.9S, #31526 on the CORE One, and #35526 on the CORE One L. The loadcell sensor returned an infinite or mathematically undefined force value, indicating the sensor circuit has lost signal integrity entirely.

What the Error Means

Unlike error 13524 (Loadcell Tare Error), which occurs when the sensor cannot zero itself, error 13526 indicates the sensor is producing a value that the firmware cannot represent — effectively a broken or saturated signal. This points to a more definitive hardware fault: either the loadcell cable has been damaged or disconnected in a way that creates a bad signal rather than no signal, or the white silicone contact pad on top of the loadcell has been physically damaged and is no longer transmitting force correctly to the sensor element. Both of these conditions cause the sensor output to rail to an unmeasurable value.

Step-by-Step Fix

1. Unload filament and power off. Remove filament and let the hotend cool below 40°C before opening any covers.
2. Remove the right-side motherboard cover. Loosen the M3 bolts securing the cover on your model — the number and location vary slightly between MK4/MK4S and CORE One. Remove the cover and set it aside.
3. Inspect the loadcell connector and cable. Examine the loadcell cable from the printhead to the xBuddy board at both connector ends and along the full cable run. Look for pinching, cuts, melted insulation, or a connector that is partially inserted. Reseat any loose connectors firmly.
4. Run the loadcell test. Power on and navigate to LCD Menu → Control → Calibrations & Tests → Loadcell Test. When prompted, tap the nozzle with your fingertip. Watch the progress bar as it fills.
5. Observe the progress bar pattern. A healthy loadcell fills the bar smoothly and quickly after the tap. If the bar fills unevenly, resets, or the test times out, the issue lies in the loadcell mechanism rather than just the cable.
6. Print the PG-assembly-adapter and disassemble the printhead. If the bar behavior is abnormal, print the PG-assembly-adapter part from Prusa’s printable parts library (print it now, before the printer fully fails). Remove the PG-case, ring, gearbox, and main-plate as a single unit following the Prusa service guide for your model. Inspect the white contact pad on top of the loadcell sensor — look for cracks, deformation, or contamination. Do not touch the pad with bare hands. If damaged, replace the pad and reassemble, ensuring the gearbox is properly realigned to the loadcell.

Parts Required

• Replacement loadcell cable (if cable is visibly damaged)
• Replacement loadcell white contact pad (if pad is cracked or deformed)
• PG-assembly-adapter (printed part — download from Prusa’s printable parts repository)

Contact Prusa Support if the error persists after the loadcell pad inspection and cable replacement — the loadcell sensor element itself may have failed and require a full printhead assembly.

Frequently asked questions

What does Prusa 13526 mean?

Prusa error 13526 (Loadcell Measure Failed) appears on the MK4 and is reported as #26526 on the MK4S, #21526 on the MK3.9, #27526 on the MK3.9S, #31526 on the CORE One, and #35526 on the CORE One L. The loadcell sensor returned an infinite or mathematically undefined force value, indicating the sensor circuit has lost signal integrity entirely.

How do I fix Prusa 13526?

Prusa error 13526 means the loadcell returned an infinite or undefined force reading. Fix cable damage and loadcell pad issues on MK4, MK4S, and CORE One.