What Size Bulbs Does a 1990 Audi 100 Use?
Correct headlight, fog light, and tail light bulb sizes. Sourced from OEM catalog data.
Installation Difficulty
Hard (Tight clearances)
Est. Replacement Cost
$15 - $40 (Halogen) / $30+ (LED)
What Lighting System Does the 1990 Audi 100 Have?
The 1990 Audi 100 features an extensive lighting system with 13 bulb positions. It uses halogen technology with a single 9004 LED dual-filament bulb handling both low and high beams. The 100 has been available from 1989 to 1994, and the 1990 model falls in the early-generation years. As a Audi vehicle, it uses a CANbus electrical system that monitors bulb status.
LED Flicker Warning
This vehicle (Audi) is known to use a CANbus system that checks for burnt-out bulbs. Installing standard LEDs may cause them to flicker or trigger a dashboard error.
We highly recommend using a CANbus decoder or "Anti-Flicker" resistors.
Can You Put LED Bulbs in a 1990 Audi 100?
Upgrading the 1990 Audi 100 to LED headlights is straightforward since it uses a single 9004 LED dual-filament bulb for both low and high beams. You only need one pair of LED bulbs to upgrade both functions. Look for a 9004 LED LED kit that specifically supports dual-filament operation to ensure both beams work correctly. Important: Audi vehicles use a CANbus system that detects bulb wattage. Standard LED bulbs may trigger dashboard warnings or flicker. Choose LED kits labeled "CANbus-compatible" or add inline decoder resistors to prevent these issues. For the fog lights, a H3 LED LED bulb provides a clean white output that pairs well with LED headlights.
How to Replace Bulbs on a 1990 Audi 100
To remove the headlight bulb, disconnect the wiring harness, then twist the bulb counter-clockwise and pull it straight out of the housing. Audi vehicles are known for tight engine bay clearances around the headlight assembly. You may need to remove the air intake duct, battery cover, or wheel well liner to access the bulbs. Budget 30 to 45 minutes per side for your first replacement. When installing the new bulb, avoid touching the glass with bare fingers. Skin oils create hot spots that shorten bulb life. Wear clean gloves or handle the bulb by its plastic base only. The fog lights are accessed from underneath the front bumper. You may need to remove a few plastic clips or screws from the fender liner to reach the H3 LED fog light socket.
Full Upgrade Bundle
Upgrade All 13 Positions at Once
1990 Audi 100 Complete Bulb Size Chart
| Position | Bulb Size | Shop |
|---|---|---|
Low Beam | 9004 LED | Buy 9004 LED |
High Beam | 9004 LED | Buy 9004 LED |
Fog Light | H3 LED | Buy H3 LED |
Brake Light | 2723 | Buy 2723 |
Dome Light | 6411 | Buy 6411 |
Side Marker | 5007 | Buy 5007 |
Turn Signal Front | 7528 | Buy 7528 |
License Plate | 3893 | Buy 3893 |
Map Light | 47830 | Buy 47830 |
Parking Light | 7528 | Buy 7528 |
Turn Signal Rear | 7506 | Buy 7506 |
Reverse Light | 7506 | Buy 7506 |
Trunk Light | 6411 | Buy 6411 |
Want to upgrade everything at once?
Shop Complete LED Kit for 1990 Audi 100How Long Do 1990 Audi 100 Headlight Bulbs Last?
Standard halogen headlights on the 1990 Audi 100 have an expected lifespan of 500 to 1,000 hours, which works out to roughly 2 to 3 years of normal use. Signs of a failing halogen bulb include noticeably dimmer output, a yellowish tint compared to the other headlight, or intermittent flickering. At 36 years old, the original bulbs on your 100 are likely overdue for replacement. Even if they still illuminate, reduced brightness significantly impacts nighttime safety. When one headlight burns out, replace both sides at the same time. Bulbs from the same batch age at similar rates, and mismatched brightness is distracting to oncoming drivers.
What Bulbs Are Compatible with the 1990 Audi 100?
The 9004 low beam bulb on the 1990 Audi 100 is a specific fitment. There are no widely recognized cross-compatible alternatives, so make sure to purchase the exact 9004 size. Using the wrong bulb size can cause improper beam patterns that reduce your visibility and blind other drivers. It can also cause overheating inside the headlight housing, potentially warping the plastic lens or reflector. Always verify the bulb number before purchasing.
1990 Audi 100 Headlight FAQ
Did Audi 100 Bulb Sizes Change Over the Years?
The Audi 100 has maintained consistent bulb sizes across all model years from 1989 to 1994. The low beam has used a 9004 LED bulb throughout, which means replacement parts and LED upgrade kits are widely available and well-tested for this model. If you find a deal on bulbs for any 100 year in this range, they will fit your 1990 model.
Other 100 Years
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Other Vehicles That Use 9004 LED Bulbs
These vehicles from other makes also use a 9004 LED low beam bulb: