The H15 bulb is a dual-function automotive lighting standard engineered to operate as both a high-beam headlight and a daytime running light (DRL) within a single bulb. It is primarily used in modern European vehicles, including platforms from Volkswagen, Audi, and BMW, where integrated lighting logic reduces component count and simplifies headlamp assemblies.
The H15 bulb operates on a 12V electrical system and uses a PGJ23t-1 keyed plastic base with three contact pins, making it physically and electrically unique. It is not interchangeable with H11, H7, or H1 bulbs due to differences in base geometry, contact layout, and dual-circuit functionality. The keyed design enforces correct polarity and alignment during installation, preventing reverse fitment.
Unlike single-beam bulbs, the H15 bulb contains two independent circuits:
- Daytime Running Light mode: ~15W, drawing approximately 1.2A
- High-beam mode: 55W, drawing approximately 4.6A
This dual-output configuration allows the vehicle’s lighting control module to switch between low-intensity DRL operation during daytime driving and full-intensity high-beam illumination at night. Because both functions share the same bulb envelope, thermal management and precise emitter positioning are critical for reliability and beam accuracy.
H15 LED Replacement Technology (30W Class)
The H15 LED headlight bulbs in this collection replace halogen filaments with solid-state LED emitters, producing light via electroluminescence at a semiconductor p-n junction. The featured H15 White LED bulbs with 30W Cree chips are designed to replicate the dual-function behavior of the original halogen H15 while improving efficiency and longevity.
Key technical attributes include:
- 30W total system power optimized for high-beam operation
- White output tuned for modern visibility standards
- Dedicated LED circuitry for high-beam and DRL functionality
- Instant 0-second illumination, unlike halogen filament ramp-up
- Reduced power draw compared to 55W halogen high-beam mode
Because many H15-equipped vehicles actively monitor bulb resistance, CANbus compatibility is critical. H15 LED retrofits without proper load simulation can trigger dashboard bulb-out warnings or DRL faults, which is why these bulbs are frequently cross-referenced with CANbus LED Headlight Bulbs and Anti-Flicker / Error-Cancellation Modules.
Housing Compatibility and Beam Control
H15 bulbs are most commonly installed in reflector-based headlamp housings, where beam spread and high-beam throw are defined by the reflector geometry rather than the bulb. Projector housings are rarely paired with H15, as the bulb’s dual-function design does not align well with shutter-based cutoff systems.
For LED H15 bulbs, emitter placement must precisely match the original halogen filament position. Misaligned LED chips can cause:
- Reduced forward throw
- Hot spots or dark zones
- Increased glare for oncoming traffic
For this reason, H15 LED upgrades are typically validated alongside a Headlight Housing Compatibility Guide and a Vehicle Bulb Fitment Lookup to ensure correct optical performance.
H15 vs Other Common Bulb Types (3 Key Differences)
- H15 vs H11: H11 is a single-beam low-beam bulb (55W); H15 is dual-function high beam + DRL
- H15 vs H7: H7 is a single-beam bulb with a different base and no DRL capability
- H15 vs H4: H4 combines high/low beams but does not support DRL circuitry
These differences make socket modification or cross-fitting unsafe and unreliable.
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