How do you fix motorized seat belt?

I have a 1990 Acura integra with retratable seat belts. My seat belt on driverside will not retract to secure position. Seat belt stays in forward position. I replaced door latch thinking this might have solved my problem, it didn't. I then checked the seat belt motor located in back quarter. I did this by disconnecting power in wire coupler. I then connected power to the wire coupler connection to the seat belt motor. The seat belt moved back to secure position. I then reversed the wires to the wire coupler connection and seat belt moved forward. By using the separate power source the seat belt moved forward and back, operating as it should. I figure the seat belt motor doesn't need to be replaced as it works fine with separte power source applied. I am wondering if there is a faulty relay switch that might be causing my seat belt from working properly. If there is a relay switch where would it be located? Is there anyone that can give me information regarding my seat belt proble? Any information would be greatly appreciated.