If the ignition switch on your Ford Mondeo fails because of an electrical fault, wear and tear or due to an attempted theft, the lock mechanism may need to be replaced. Removing the lock mechanism itself is easy but involves disconnecting a number of components that must be dealt with in the correct order. This will make refitting easier and prevent damage to any of the vehicle's electrical systems.
Disconnect the negative lead from the battery. Wait at least 10 minutes before doing anything else to ensure the energy in the back-up capacitor is dissipated. This will prevent the airbag from firing accidentally.
Align the front wheels in the straight-ahead position. Rotate the steering wheel so one of the airbag mounting bolt holes is visible above the upper shroud of the steering column. Unscrew and remove the first bolt, turn the steering wheel through 180 degrees and remove the remaining bolt. Carefully remove the airbag unit and disconnect the wiring clips.
Insert the ignition key to make sure the steering lock is disengaged. Unscrew the retaining bolt from the center of the steering wheel and remove the steering wheel from the top of the column. Carefully feed the wires from the horn and airbag through the hole in the steering wheel as you remove it.
Remove the lower fascia trim panel on the driver's side by remove the four screws. If the car is fitted with climate control you will also need to disconnect some additional wiring as the panel is removed. If the car has audio controls built into the steering wheel, these will need to be disconnected by using a small screwdriver to release the plastic locking clip.
Remove the upper shroud of the steering column from the lower shroud by inserting a thin screwdriver between the clip on each side. Undo the three screws and remove the lower shroud. Undo the retaining screw that holds the Passive Anti-Theft System transceiver in place and remove it. Use a screwdriver to release the clips holding the ignition switch in place and remove it, disconnecting the wiring as you do.
Insert the ignition key and turn it to position I. Using a small screwdriver, depress the catch in the lock housing and remove the ignition lock cylinder. To fit a new lock, follow the removal steps in reverse, taking care to reconnect all necessary wiring.
It may be possible to access the switch without removing the steering wheel, but removal makes the job much easier.
Ensure that you remove the key from the ignition before reconnecting the battery and place it in your pocket or in a safe place outside the car. This is because the central locking mechanism will engage when the battery is reconnected, locking you out of the vehicle.