Prusa Error 13321: Power Panic Detected on Startup
LayerWalker is a participant in the Amazon Services LLC Associates Program. We may earn a commission when you buy through links on our site, at no extra cost to you.
Prusa error 13321 means the power panic circuit reported a fault at startup, and Prusa’s own text says to check the power panic cable. That circuit detects mains loss and parks the print head so a resumed print lines up afterwards. The cable is the commonest cause, and it is the one most often left unplugged after working in the electronics bay.
Power panic is easy to ignore because the printer still prints without it. What you lose is the ability to survive a power cut mid-print — which on a twelve-hour job is the difference between resuming and starting again.
Where to buy
Check in this order
- The power panic cable. Reseat it at both ends. If you have recently had the electronics bay open, this is almost certainly it.
- Look for damage. A pinched cable where the cover closes produces an intermittent version of the same fault.
- Mains stability. Brownouts trip the detector legitimately. If your supply dips when a kettle or a workshop tool starts, the printer is reporting something real.
- The power supply. A PSU sagging under load looks like a mains dip to the detector, often first noticeable as the heatbed failing to preheat. Worth suspecting if the error appears under heavy heating load rather than at startup.
Whether to add a UPS
If your mains genuinely dips, a modest UPS removes the whole class of problem — and it does so more reliably than power panic, which recovers a print rather than preventing the interruption. For a printer running long jobs unattended, it is one of the few accessories that pays for itself in a single saved print. Where it sits against other purchases is in accessories worth owning.
Related codes
13309 and 13308 are overcurrent faults, which are about too much current rather than too little voltage. The same power panic error reads 31321 on CORE One, 17321 on XL, 35321 on CORE One L and 23321 on MK3.5.
Prusa Error 13321 FAQ
Can I print with error 13321?
Usually yes, after dismissing it, but you lose power-loss recovery. On short prints that is a small risk; on long ones it is not.
What does power panic actually do?
It detects the supply failing, parks the head clear of the print and records the position, so the printer can resume from the same point rather than restarting.
Why did this appear after I opened the printer?
Because the power panic cable is the one most often left unplugged or pinched during reassembly. Check it before anything else.
Does a UPS replace power panic?
It does something better — it prevents the interruption rather than recovering from it. But fix the cable anyway; the two protect against different failures.
LayerWalker
Print defect diagnosis, calibration procedures and parts that actually fit. Corrections welcome through the contact page.
