The fusing thermopile (TH2) [A] monitors the surface temperature at the center of the hot roller. If the temperature exceeds 245°C (475°F), the machine cuts off the power to the fusing lamps [C].
The fusing thermistor (TH1) [B] monitors the temperature at the end of the hot roller. If the temperature exceeds 245°C (475°F), the machine cuts off the power to the fusing lamps [C].
If the machine overheats it will issue S543/SC553, and then stop. A customer engineer must release SC543/SC553 with SP5-810-001 to restore operation of the machine.
Two thermostats, thermostat (center) (TH4) [D] and thermostat (end) (TH3) [E] provide more protection from overheating in case either one or both fusing thermopile (TH2) [A] and fusing thermistor (TH1) [B] should fail. These thermostats monitor the temperature around the hot roller and will cut off the power to the fusing lamps and shut down the machine if the temperature exceeds 350°C (662°F).
