• Code: C3421
• Description: Fusing warm-up trouble (Middle of the heating roller). Detected temperature of the thermistor/1 (TH1) or thermistor/2 (TH2) does not go up a given range of temperature even after a lapse of given period of time at warm up.
• Causes: • Fusing unit • Thermistor/1 (TH1) • Thermistor/2 (TH2) • DC power supply (DCPU) • MFP board (MFPB)
• Remedy: 1. Check the fusing unit for correct installation (whether it is secured in position). 2. Check the open/close operation of the right door. 3. Check the connector between the fusing unit-relay CN19-MFPB CN18E for proper connection and correct as necessary. 4. Check the connector between the fusing unit-relay CN7AC-DCPU CN2 for proper connection and correct as necessary. 5. Check the connector between MFPB CN2E-DCPU CN7 for proper connection and correct as necessary. 6. Replace the fusing unit. 7. Replace MFPB. 8. Replace DCPU.

• Code: C3721
• Description: Fusing abnormally high temperature detection (Middle of the heating roller). Detected temperature of the thermistor/1 (TH1) goes beyond a given temperature for a given period of time consecutively.
• Causes: • Fusing unit • C3721: Thermistor/1 (TH1) • C3722: Thermistor/2 (TH2) • MFP board (MFPB)
• Remedy: 1. Check the fusing unit for correct installation (whether it is secured in position). 2. Check the open/close operation of the right door. 3. Check the connector between the fusing unit-relay CN19-MFPB CN18E for proper connection and correct as necessary. 4. Replace the fusing unit. 5. Replace MFPB.

• Code: C3722
• Description: Fusing abnormally high temperature detection (Edge of the heating roller). Detected temperature of the thermistor/2 (TH2) goes beyond a given temperature for a given period of time consecutively.
• Causes: • Fusing unit • C3721: Thermistor/1 (TH1) • C3722: Thermistor/2 (TH2) • MFP board (MFPB)
• Remedy: 1. Check the fusing unit for correct installation (whether it is secured in position). 2. Check the open/close operation of the right door. 3. Check the connector between the fusing unit-relay CN19-MFPB CN18E for proper connection and correct as necessary. 4. Replace the fusing unit. 5. Replace MFPB.

• Code: C3731
• Description: Fusing abnormally high temperature detection (Hard protector). The hard protector signal error is detected for a given period of time consecutively.
• Causes: • Fusing unit • Thermistor/1 (TH1) • Thermistor/2 (TH2) • MFP board (MFPB)
• Remedy: 1. Check the fusing unit for correct installation (whether it is secured in position). 2. Check the open/close operation of the right door. 3. Check the connector between the fusing unit-relay CN19-MFPB CN18E for proper connection and correct as necessary. 4. Replace the fusing unit. 5. MFPB F3E conduction check 6. Replace MFPB.

• Code: C3821
• Description: Fusing abnormally low temperature detection (Middle of the heating roller). Detected temperature of the thermistor/1 (TH1) goes below a given temperature for a given period of time consecutively after warm up is completed.
• Causes: • Fusing unit • C3821: Thermistor/1 (TH1) • C3822: Thermistor/2 (TH2) • MFP board (MFPB)
• Remedy: 1. Check the fusing unit for correct installation (whether it is secured in position). 2. Check the open/close operation of the right door. 3. Check the connector between the fusing unit-relay CN19-MFPB CN18E for proper connection and correct as necessary. 4. Replace the fusing unit. 5. Replace MFPB.

• Code: C3822
• Description: Fusing abnormally low temperature detection (Edge of the heating roller) Detected temperature of the thermistor/2 (TH2) goes below a given temperature for a given period of time consecutively after warm up is completed.
• Causes: • Fusing unit • C3821: Thermistor/1 (TH1) • C3822: Thermistor/2 (TH2) • MFP board (MFPB)
• Remedy: 1. Check the fusing unit for correct installation (whether it is secured in position). 2. Check the open/close operation of the right door. 3. Check the connector between the fusing unit-relay CN19-MFPB CN18E for proper connection and correct as necessary. 4. Replace the fusing unit. 5. Replace MFPB.

• Code: C3921
• Description: Fusing sensor wire breaks detection (Middle of the heating roller) The maximum value and minimum value of detected temperature of the thermistor/2 (TH2) is compared after a lapse of given time from starting of warm up and the gap between the value of maximum and minimum is below a given temperature.
• Causes: • Fusing unit • C3921: Thermistor/1 (TH1) • C3922: Thermistor/2 (TH2) • MFP board (MFPB)
• Remedy: 1. Check the fusing unit for correct installation (whether it is secured in position). 2. Check the open/close operation of the right door. 3. Check the connector between the fusing unit-relay CN19-MFPB CN18E for proper connection and correct as necessary. 4. Replace the fusing unit. 5. Replace MFPB.

• Code: C3922
• Description: Fusing sensor wire breaks detection (Edge of the heating roller) The maximum value and minimum value of detected temperature of the thermistor/2 (TH2) is compared after a lapse of given time from starting of warm up and the gap between the value of maximum and minimum is below a given temperature.
• Causes: • Fusing unit • C3921: Thermistor/1 (TH1) • C3922: Thermistor/2 (TH2) • MFP board (MFPB)
• Remedy: 1. Check the fusing unit for correct installation (whether it is secured in position). 2. Check the open/close operation of the right door. 3. Check the connector between the fusing unit-relay CN19-MFPB CN18E for proper connection and correct as necessary. 4. Replace the fusing unit. 5. Replace MFPB.