Dave, H4 is low fuser temperature, remove the fuser by opening left hand door, then from the front, remove two screws holding in the fuser unit. When out remove two screws on top to take off cover, from memory should be a resetable thermal fuse, which should click when pressed if blown. re-assemble. To reset the code press these buttons:cancel, interupt, zero interupt, (display will go dead) enter 14, print, 1 print, should reset.
good luck, Andy
Andy B, January 2010