The headlamp assembly uses a separate replaceable quartz halogen bulb for the low beam and the high beam. Refer to Specifications → Specifications: 2006 FLHTCUSE Model → Bulb Chart: 2006 FLHTCUSE and see a service manual for more details.
To replace the bulbs:
  1. See Figure 1. Remove the small fastener and the headlamp door.
  2. See Figure 2. Remove the 3 screws and the reflector/lens retaining ring (1).
  3. Support the reflector/lens and remove the wire harness connectors from the bulb connectors.
  4. Quarter turn the connector to remove a bulb from the reflector/lens.
  5. Quarter turn a new bulb to lock the bulb in the relector/lens and mate the wiring harness connectors to the bulb connectors.
  6. Set the reflector/lens up to the adjustment ring matching the square tabs to the square recesses in the ring.
  7. Align the three taps on the retaining ring with the threaded holes on the adjustment ring and tighten to hold the reflector/lens in place.
  8. Replace the headlamp door and tighten the fastener.
NOTE
Refer to Maintenance and Lubrication → Headlamp Alignment: FLHTCUSE if the headlamp beam requires adjustment.
NOTICE
When replacement is required, use only the specified sealed beam unit or bulb, available from a Harley-Davidson dealer. An improper wattage sealed beam or bulb, can cause charging system problems. (00209a)
NOTICE
Never touch the quartz bulb. Fingerprints will etch the glass and decrease bulb life. Handle the bulb with paper or a clean, dry cloth. Failure to do so could result in bulb damage. (00210b)
WARNING
Handle bulb carefully and wear eye protection. Bulb contains gas under pressure, which, if not handled carefully, could cause serious eye injury. (00062b)
1Fastener
2Headlamp door (chrome ring)
3Vertical adjustment
4Horizontal adjustment
Figure 1. Headlamp Door: FLHTCUSE
1Retaining ring fastener
2Headlamp adjusting screw
Figure 2. Headlamp Retaining Ring: FLHTCUSE