Fuji Xerox Phaser 5500 Service Manual page 63

Power Shutoff to the Fuser
The printer shuts off power to the Fuser for the following reasons:
Fuser abnormality (U4)
Paper jam
Cover Open - Doors A, B, C, D, Front Door
Laser Assembly abnormality (U3)
CPU or NVRAM abnormality (U6)
Motor Assembly abnormality (U0, U1)
Fuser Fan abnormality (U4)
Fuser Problems (U4 Error Code)
Causes of Fuser errors include:
During the Warm-Up period, the Control Thermistor does not detect the Ready
temperature even when the specified time has passed.
During the Standby period, the Control Thermistor does not detect the required
temperature even when the specified time has passed.
During the Standby period, the Control Thermistor does not detect the required
temperature even when the specified time has passed.
During idling after power-on, the Control Thermistor does not detect the idling
stop temperature even after the specified time has passed.
During print, the Control Thermistor does not detect the required temperature
even when the specified time has passed.
During print, the Control Thermistor does not detect the required temperature
even when the specified time has passed.
Fuser Temperature Regulation
Fuser temperature regulation is managed by the Engine Logic Board with input from
the Fuser's temperature sensors. The Fuser transits between four operating modes,
Warm-up, Ready, Print, and Low Power. Transitions between these four modes is
dependent on Heat and Pressure Roller surface temperature or printer conditions.
Fuser temperature regulation begins when the Fuser relay on the Low Voltage Power
Supply (LVPS) is switched to apply AC power to the Heat Rods. If the Ready
temperature is not reached within the Warm-up delay period, the Heater Rods are
turned Off, the Fuser relay is turned Off, and Fuser temperature control is stopped.
Theory of Operation 2-23