BMW Headlight Low/High beam Malfunction Explained
Broken headlight bulb
Different headlight types and different headlight bulbs have different life spans, so if one of your bulbs is broken it will most likely have blown or burnt out as Xenon HID bulbs also known as Gas Discharge bulbs have certain working hours for every different brand and model.
The same life span feature applies to halogen bulbs as well.
The most common Xenon bulb used for BMW cars are 35W D1S and D2S type as mostly bimmers are factory fitted only with projector headlamps.
For BMW halogen headlight the most popular light bulb is H7 477 2 PIN type and it is used only in the halogen / reflector type headlamp units.
Any brand bulbs for example Philips, GE, Osram, Neolux, Narva, Hella etc. could be fitted just make sure you are buying correct fitting (socket) bulbs.
Faulty xenon light control unit
Another the most common xenon headlamp issue causing the low or high beam malfunction is faulty ballast also known as xenon light control unit.
Usually it is some kind of square or rectangular shape small box attached onto the side or either bottom of the headlight housing.
To identify faulty ballast you need to try new HID bulb or change sides from working side, if lights don't work after replacing lamp - it means that control unit is to blame.
The most common failure sympthom of this part is that bi-xenon lights keep blinking and flickering, shutting down later turning on after re-turing on / off lights manually or lights stop to work suddenly out of no where, then it is big indication to check this part at the first possible opportunity, because diagnostics trouble codes (DTC) won't show if gas discharge HID bulb or ballast has failed - it always show just generic error code (fault) that headlights have malfunction.
The most popular xenon ballast brands BMW cars are using: Hella, Valeo, Mitsubishi Electric and Automotive Lighting AL (Bosch).
If two of your headlights have stopped working at the same time, it is much more likely that a fuse has blown than both the bulbs. If a bulb has been attached to the car with the wrong wattage or too much current is in the headlight circuit, the fuse will blow to protect the wiring from damage.
Poor light quality
If your headlights are still emitting light but not at their usual strength, it may be that your car is experiencing headlight fogging. Headlight fogging is caused when polycarbonate is exposed to ultraviolet light and exhaust emissions, as a chemical reaction occurs which causes the headlights to fog up. With headlight fogging, the light released from the headlight is hard to see even when both the high and low beams are switched on.
A list of xenon ballasts part numbers used for BMW cars:
- AL 1 307 329 317 00 - 130732931700 Al01 Zlc
- AL 1 307 329 318 00 - 130732931800 - 10EEG120223 Al01 Zlb
- AL 1 307 329 263 01 - 130732926301 - 10EEG111387 Al01 Zld
- AL 1 307 329 318 15 - 130732931815 - 10EEG141019
- AL 1 307 329 317 15 - 130732931715 - 10EEG141013 Al02 Zle
- AL 1 307 329 461 00 - 130732946100 - 10EEG120224 Al01 Zla
- Mitsubishi Electric W003T20071
- Mitsubishi Electric W003T23171
- Mitsubishi Electric W003T19571
- Hella 5DV 009 000-00 - 5DV009000-00
- Hella 5DV 008 290-00 - 5DV008290-00
- Hella 5DV Xenus 009 610-00 - 5DV009610-00
- Valeo 6G 89034934 Ballast6G
BMW part numbers for control units:
- 63127296090 - 7296090
- 63117237647 - 7237647
- 63117318327 - 7318327
- 63127172536 - 7172536
- 63117317408 - 7317408
- 63127255724 - 7255724
- 63126907488 - 6907488
- 63120150614 - 0150614