Here's a general outline of the process. Always consult a repair manual specific to your 1990 Grand Marquis for detailed instructions, diagrams, and torque specifications. These vary slightly depending on the trim level and options.
Tools You'll Likely Need:
* Repair Manual: Absolutely essential.
* Socket Set: Various sizes, including metric and possibly SAE.
* Screwdrivers: Phillips and flathead, various sizes.
* Pliers: Needle-nose and regular.
* Wrench Set: Possibly needed depending on your specific car.
* Ignition Switch Removal Tool: This special tool helps remove the old switch without damaging the ignition cylinder. You might be able to improvise, but the tool greatly reduces the risk.
* Electrical Tape: To secure wires.
* Penetrating Oil (like PB Blaster): To help loosen any corroded screws or connections.
General Steps (Consult your repair manual for precise details):
1. Disconnect the Battery: This is the most crucial first step to prevent electrical shorts and injury. Disconnect both the positive (+) and negative (-) terminals.
2. Steering Wheel Removal (Possibly): Depending on your Grand Marquis's specific setup, you might need to remove the steering wheel to access the ignition switch. This is a complex step requiring a steering wheel puller and specialized knowledge. Again, your repair manual is critical here.
3. Column Shroud Removal: Remove the plastic shroud surrounding the steering column. This usually involves removing screws and possibly some clips.
4. Ignition Lock Cylinder Removal: This is often a separate component from the ignition switch itself. You'll need to remove the ignition lock cylinder before you can access the switch. This typically involves removing the lock cylinder retaining ring and carefully pulling the cylinder out.
5. Wiring Harness Disconnection: Carefully disconnect the wiring harness from the old ignition switch. Take pictures or make notes of the wiring configuration before disconnecting anything to aid in reassembly.
6. Ignition Switch Removal: Use the ignition switch removal tool (or your carefully devised method) to remove the old ignition switch from the steering column.
7. Installation of the New Switch: Carefully install the new ignition switch, ensuring it's properly seated.
8. Wiring Harness Reconnection: Reconnect the wiring harness to the new ignition switch, precisely matching the connections from your notes or pictures.
9. Ignition Lock Cylinder Reinstallation: Carefully reinstall the ignition lock cylinder.
10. Reassembly: Reassemble the column shroud, steering wheel (if removed), and reconnect the battery.
11. Testing: Turn the key to ensure the ignition switch functions correctly, starting the engine and checking all electrical components.
Important Considerations:
* Matching the Switch: Ensure you purchase a replacement ignition switch that is the correct part number for your specific 1990 Grand Marquis model.
* Key Programming: In some cases, you might need to have your new ignition switch programmed to work with your car keys.
* Professional Assistance: If you are uncomfortable with any part of this process, it's strongly recommended to take your vehicle to a qualified mechanic. This is not a simple job, and mistakes can be costly.
This is a generalized guide. The specific steps and difficulties will depend on your car. Always refer to a repair manual specific to your 1990 Ford Grand Marquis before beginning this repair. Failure to do so could lead to damage to your vehicle or personal injury.
