I have a 1990 Mustang LX 5.0 and on the driverside where the seat goes is a square green color electrical connection that gets plugged in. Anyone know what this connector is?
Right, and the car won't start with it unplugged. Why they put it under the seat I have no idea. Just remember to plug it back in if you take it out to clean your carpet under there.
Sounds like you are talking about the connector itself, not the relay. If that's the case, you may need to get one from a junkyard so you can unclip the wires and switch them to the good connector.