Old rear wiper motor to new wiper swap... wiring issues.

Ok so the rear hatch wiper motor died in the 88' xj. Had a spare out of a mid 90's on hand so sweet deal right? nope, the 88 motor has 3 leads coming out of the harness, while the new motor has four, and an relay assembly that the old motor didnt have... now anybody know for sure how to wire it up so it works? I have sat down with jumpers and on normal wipe mode i can get it to run in the usual 5 or so sec pattern, go to the other jumper and it runs constant (wash mode i assume) but i can only get a power to it with the dash switch in just run. Plus if i hook it up to just run mode when it's off on the dash the relay still clicks but the motor doesnt run... do i need to follow the harness on the jeep back to the relay for the orignal motor and eliminate it since there is a relay on the new motor? Im a wiring ingoramous so any help that is verry dumbed down is appreciated.:dunce:

Thx