Not the bulb. Xenon is same brightness all the time. There is a shield that moves via electrical signal to allow full exposure for high beam. Check wiring or maybe solenoid is stuck.

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Dave

'05 325xi
'10 E70 35d
'85 911 Carrera
'66 911 Work in progress
'91 Chevy C1500
'95 Jeep Cherokee
‘18 Jeep JLU