My WC7545 is giving me "Fuser Sytem Error" on main GUI. When I looked in diagnostic faults it said 310-330 fuser motor fault. Tested connections no +5vdc. Replaced fuser motor, and it was still jamming at fuser intermittently but i could still print. Swapped out fuser with another. Printer GUI still has "Fuser system error" but the only fault i am getting in diagnostic faults is 310-378 Heat Belt Rotation Fault. Now it wont print at all GUI is saying "no printing or copying available".
It looks like even the 2nd fuser is faulty. The fault codes are from a hard rotating of fuser belt.Try to remove the fuser cover and you will see 2 adjusting screws with spring. Unscrew them until the plates come in touch. When you put back the cover pay attention at the sensor actuator to be in place and to not broken it.