Part numbers:
Xerox Phaser 4500 - 604K14921, 604K14923, 604K1493, 604K19443, 604K28530, 604K28531, 604K28532, 604K28533, 604K285332, 604K28534
Xerox Phaser 4510 - 126K23786, 604K37276, 604K37338, 604K37339, 604K50470, 604K50471, 604K57440

Common error codes:
U4-1 = Fuser high temperature
U4-2 = Fuser low temperature
U4-3 = Fuser overheat
U4-4 = Fuser fails at warm-up
U4-5 = Fuser Thermistor Failure

Compatible models:
Phaser 4500N
Phaser 4510N