Ford Mustang Wiring Diagram for 1987-1993 Instrument Cluster
If you are attempting to install a 1990-1993 steering wheel in a 1987-1989 car, then the steering column must also be changed. All connections will hook up in the steering column except for the harness from the steering wheel, which provides the horn and cruise control signal. The windshield wipers will not work if the 1990-1993 switch is used on the 1987-1989 harness. Testing with a multimeter will show you the wires that Ford chose to move when the design of the switch changes. All controls have the same wiring except the windshield wipers. After the correct wires are determined, it is an easy task to remove the wires from the plug by pressing down on the tab on the front of the plug and sliding the wire out the back. Then, the wire can be inserted into the previously unused connection hole on the plug.
This process if much easier if you have an old harness from a 1990-1993 that comes out of the instrument cluster. The wires need to be as long as possible (6-8 inches), and they can be successfully wire tapped and soldered to the factory 1987-1989 harness.
