Ford 2003 Mustang Owner's Manual page 179

Maintenance and care
To install the new bulb:
1. Install the electrical
connector into the rear
of the plastic base until
it snaps, locking it into
position.
2. With the flat side of the bulb's plastic base facing
upward, insert the glass end of the bulb into the
lamp assembly. You may need to turn the bulb left or
right to align the grooves in the plastic base with the
tabs in the lamp assembly. When the grooves are
aligned, push the bulb into the lamp assembly until
the plastic base contacts the rear of the lamp
assembly.
3. Install the bulb retaining ring over the plastic base
until it contacts the rear of the socket by rotating
clockwise until you feel a "stop".
4. Turn the headlamps on and make sure they work
properly. If the headlamp was correctly aligned
before you changed the bulb, you should not need to
align it again.
High-mount brakelamp bulbs
The following
procedure is for sedans
only. For wagon, refer
to a qualified
technician.
1. Open trunk.
2. Inside trunk, locate
access hole under the
rear window
3. Remove the bulb
socket by rotating it 45 degrees and pulling it out of
the lamp assembly.
4. Carefully pull bulb straight out of socket and push
in new bulb.
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