The wiring on the heater fan motor has broken right at the grommet where it exited the housing so I decided to replace it. I took the housing apart, soldered on new, color-coded wires and pulled them through the old grommet. Then I soldered on bullet connectors and a terminal for the ground screw.
Get as many of these little projects done on the heater box as you can because it is kind of a pain to remove. You may even consider replacing your heater core.
Main Heater Collar Page