Error 50.4 on HP printers means the fuser unit has failed to reach the correct operating temperature within the expected time. This stops all printing until resolved.
The fuser is the component that bonds toner powder to paper using heat and pressure. Without a working fuser, toner sits loose on the page and wipes off easily. The fuser must reach around 180-200 degrees Celsius to function correctly.
A faulty power supply delivering insufficient voltage to the fuser is the most common cause. A failing fuser unit itself is the second most common cause. On some models, a bad low-voltage power supply causes intermittent 50.4 errors.
Turn off the printer and unplug from the wall. Wait 30 minutes — this allows the fuser to cool completely. Plug in and restart. If the fuser was simply overheated, this resolves the error.
Plug the printer directly into a wall outlet — not a power strip or UPS. Some power strips do not deliver sufficient amperage for laser printer fusers, causing error 50.4.
If power cycling does not resolve the error, the fuser unit needs replacement. HP fusers are model-specific — ensure you purchase the correct fuser for your exact printer model. Compatible fusers are available at significantly lower cost than OEM units and perform identically.
If a new fuser does not resolve error 50.4, the low-voltage power supply board may be faulty. This requires professional diagnosis.
Affected Models: HP LaserJet 4000, 4050, 4100, 4200, 4250, 4300, 4350, P4014, P4015, P4515, M601, M602, M603.
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