The Peterbilt 320 front turn signal bulb size includes 2057 and 198 options, while rear turn signal bulb size encompasses 1157, 2057, and 198 specifications. The replacement chart covers 1987 through 2017 vehicle production years with corresponding bulb size data.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 2057 bulb is the most frequently specified type across the turn signal positions on the Peterbilt 320, appearing in front turn signal applications from 1987 through 2009 and in rear turn signal applications across much of the same span.
The 2057 is a dual-filament bulb rated at 12V with a high filament draw of 26.9W and a low filament draw of 8W, mounted on a BAY15d bayonet base, which is the same base type used by the 1157.
Because the 2057 and 1157 share the BAY15d bayonet base, they are physically interchangeable in terms of socket fit, but their wattage ratings differ. The 1157 draws 21W on the high filament and 5W on the low filament, making it a lower-output bulb than the 2057.
The rear turn signal position on the Peterbilt 320 transitions from the 2057 specification to the 1157 for model years 2011-2017, reflecting a change in the specified output level for that position in later production years.
The 198 is a single-filament miniature wedge bulb of the T5 type, rated at 12V and 2W, which places it in a substantially different output and construction category than either the 2057 or the 1157.
On the Peterbilt 320, the 198 bulb appears as a conditional fitment tied to specific headlamp configurations, including vehicles equipped with 4 rectangular headlamps or halogen capsule headlamps, rather than as a universal specification for a given model year.
For the 1992-1995 model years, both the front and rear turn signal positions list dual fitment entries, where the 198 applies to halogen capsule headlamp configurations and the 2057 applies otherwise, indicating that the headlamp system type determines the correct turn signal bulb.
The 1993 rear turn signal specification reverses the conditional logic seen in other years, listing the 198 as the standard fitment and the 2057 as the variant associated with halogen capsule headlamps.
The 198 wedge bulb does not use a bayonet base and is not interchangeable with the 2057 or 1157 despite appearing in the same turn signal position on certain configurations of the same vehicle.
All three bulb types listed in these specifications, the 2057, 198, and 1157, conform to ANSI standards applicable in both the United States and Canada.