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Here are the diagrams you are asking for. Some other things to check if the fuse is good, the only possibilities are the dimmer switch(located on the steering column), or the headlight switch. For the wires with the corrosion you can pour Coke on them then rinse with water brush away any corrosion not dissolved by the coke, then coat the wires with grease to prevent the corrosion from returning. If you have any other questions, please don't hesitate to ask.
The high beam indicator staying on makes me think most likely that the dimmer switch could be bad, as for the coke, to be safe you can just make sure everything is turned off, or disconnect the battery first. If the harness was fried, it would have blown a fuse so I doubt that is the problem. If you have access to a voltmeter, you can test for voltage at the headlights. most likely the dimmer switch is at fault, but the corrosion could have caused the switch to go bad also, by creating too much resisatance in the circuit. I recommend that you clean up all the corrosion then check the dimmer switch.
After doing a little research, the thunderbird has a combination turn signal, dimmer, and wiper switch, the switch is actually connected to the turn signal lever. If you cannot access the switch by removing the trim around the column, you may need to remove the steering wheel to access the switch. Good Luck.
Disconnect the negative battery cable.
Tilt the steering column to its lowest position, then remove the tilt steering column lock lever.
Remove the ignition switch lock cylinder, as outlined in this section.
Unfasten the shroud screws, then remove the upper and and lower steering column shrouds.
Remove the two self-tapping screws retaining the multi-function switch to the steering column tube flange. Disengage the switch from the steering column tube flange.
Detach the two switch electrical connectors.
Fig. 1: Multi-function switch and related components-1994-97 vehicles
Install the two electrical connectors to full engagement.
Align the multi-function switch mounting holes with the corresponding holes in the steering column tube flange. Install the two self-tapping screws, making sure to start the screws in the previously tapped holes. Tighten the screws to 18-26 inch lbs. (2-3 Nm).
Install the upper and lower steering column shrouds, then secure with the retaining screws.
Install the ignition switch lock cylinder.
Install the tilt steering lock lever.
Connect the negative battery cable, then check the steering column for proper operation.