Prusa error 13308 (Nozzle Heater Overcurrent) appears on the MK4 and as #21308 on the MK3.9. The Buddy board detected that the current flowing through the hotend heater circuit exceeded the safe operating limit, causing an immediate print halt to protect the electronics and prevent a fire risk.

What the Error Means

The xBuddy board monitors heater current at all times. A heater cartridge that has developed an internal short between its resistance wire and the outer sheath will draw far more current than a healthy cartridge, triggering this overcurrent fault. Physical damage to the heater cable — from a tight cable routing bend, contact with the hot nozzle block, or pinching — can create a partial short that shows up as overcurrent. In rarer cases, the fault lies on the LoveBoard or xBuddy board itself, where a switching component has failed and is allowing excessive current even through a healthy cartridge.

Step-by-Step Fix

1. Power off the printer and let it cool completely. Overcurrent events can stress components — give the electronics at least 15 minutes before inspection.
2. Inspect the hotend heater cable. Trace the two-wire heater cable from the nozzle assembly up through the cable chain to the LoveBoard connector. Look for bare wire, cracked insulation where the cable bends tightly, or any section where the cable may have contacted the hot nozzle block or print surface.
3. Disconnect and reconnect the heater connector on the LoveBoard. Unplug the heater cable from the LoveBoard and inspect the connector pins. Reseat the connector firmly.
4. Measure heater cartridge resistance with a multimeter. With the heater cable disconnected from the LoveBoard, measure resistance between the two heater leads. A healthy 40W heater cartridge typically reads approximately 3–4 Ω. A reading near zero indicates a short within the cartridge — replace it.
5. Check the main cable between LoveBoard and xBuddy board. If the heater cartridge resistance is normal but the error returns, inspect the umbilical cable for chafing or crushing damage.
6. Contact Prusa Support if wiring is intact. If the heater cartridge measures correctly and all wiring is undamaged, the LoveBoard or xBuddy board may have a failed switching component.

Parts Required

• Replacement hotend heater cartridge (if cartridge resistance is near zero or shorted)
• Replacement LoveBoard (if board is confirmed faulty — contact Prusa Support)
• Digital multimeter

If the error returns after replacing the heater cartridge, contact Prusa Support at help.prusa3d.com with your multimeter findings.

Frequently asked questions

What does Prusa 13308 mean?

Prusa error 13308 (Nozzle Heater Overcurrent) appears on the MK4 and as #21308 on the MK3.9. The Buddy board detected that the current flowing through the hotend heater circuit exceeded the safe operating limit, causing an immediate print halt to protect the electronics and prevent a fire risk.

How do I fix Prusa 13308?

Prusa error 13308 means an overcurrent was detected on the hotend heater circuit. Learn how to inspect the heater cable, LoveBoard, and xBuddy board connections.