Peterbilt 579 high beam headlight uses 9005XS bulb size while low beam headlight uses H7, D1S, or H11 bulb sizes. The replacement bulb chart covers 2013 to 2020 production years with corresponding size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 9005XS bulb serves as the high beam headlight across all listed Peterbilt 579 model years, spanning 2013-2020. The 9005XS is a compact variant of the standard 9005 bulb, sharing the same electrical base and output characteristics but housed in a physically shorter envelope, which suits assemblies with tighter internal clearances.
The low beam headlight position on the Peterbilt 579 accommodates two distinct lighting technologies depending on the installed headlamp system: halogen capsule headlamps and HID (High-Intensity Discharge) headlamps. These two systems are not interchangeable, and the correct replacement bulb depends entirely on which headlamp type is fitted to the vehicle.
For halogen low beam applications, the 2013-2019 model years predominantly use the H11 bulb, while the 2018 and 2020 model years specify the H7 bulb instead. The H11 and H7 are both single-filament halogen bulbs but use different connector types and are not cross-compatible with each other.
The H11 bulb operates on an L-shaped connector base classified as a PGJ19-2 fitting. The H7 bulb uses a PX26d base with a two-pin connector. Because these bases differ physically, an H7 cannot be seated into an H11 socket without modification, and vice versa.
HID low beam applications across all listed years, 2013-2020, uniformly specify the D1S bulb. The D1S is a discharge arc bulb that requires a compatible ballast to regulate the high-voltage ignition and sustained arc current. It cannot function in a standard halogen socket.
The D1S bulb uses a projector-style quartz envelope with an integrated igniter, distinguishing it from D2S bulbs, which use an external igniter. Substituting a D2S in place of a D1S is not electrically or mechanically compatible without replacing the associated ballast and housing components.
The 2020 model year is notable in that its halogen low beam specification shifts from H11 to H7, while the 2018 model year also carries an H7 specification. Owners of 2020 or 2018 vehicles with halogen headlamps who reference H11 fitment data from adjacent years would be selecting an incorrect bulb.
The 9005XS high beam bulb uses the same SB base as the standard 9005 and is electrically compatible with 9005 sockets. However, the shortened bulb body of the 9005XS is specific to assemblies designed around that reduced length, and installing a full-length 9005 may not be physically possible in those housings.
The coexistence of halogen and HID low beam options across the same model years indicates that the Peterbilt 579 was offered with different headlamp assemblies during production. The headlamp assembly type, not the model year alone, determines the correct low beam bulb specification.
D1S bulbs operate at a color temperature typically ranging from 4,200 to 6,000 Kelvin depending on the manufacturer, producing a whiter or bluish-white light output compared to the warmer yellow-white output of H7 and H11 halogen bulbs, which generally fall between 3,000 and 3,200 Kelvin.