Brother HL-3450CN Service Manual page 306

H2,H3,H4
Error Code
Concerned Part Fusing Unit and Others
Confirm that a fusing heater is lit.
Is the fusing heater controlled for On/Off.
YES
NO
Is the line voltage to be the default value ?
YES
NO
Is the rating of fusing heater correct ?
Are H2,H3 and H4 errors cleared ?
NO
Replace the fusing unit.
Are H2,H3 and H4 errors cleared ?
YES
Job is complete.
NO
Confirm the input voltage.
Confirm the rating and replace
the fusing heater.
YES
YES
NO
YES
Confirm the wiring and connector of the heater.
Is the connector HP/HN connected ?
YES
Is the fusing unit properly installed ?
YES
Is the fuser connector damaged ?
NO
Is there any contract failure of the lamp holder ?
NO
Is the heater wiring cut or damaged ?
NO
Are H2,H3 and H4 errors cleared ?
NO
Replace the power supply unit (LVPS).
Are H2,H3 and H4 errors cleared ?
NO
Replace the MCTL PWB.
8-43
HL-3450CN SERVICE MANUAL
NO
Connect them properly.
NO
Install it properly.
YES
Replace the connector.
YES
Replace the lamp and lamp holder.
YES
Replace the heater.