Peterbilt 320 front side marker bulbs use 194 size while rear side marker bulbs use 1816 size. The replacement chart covers vehicle production spanning 1987 to 2009.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Peterbilt 320 front side marker position uses the 194 bulb across all listed model years from 1987 to 2009.
The 194 is an ANSI-standard miniature wedge bulb in the T10 form factor, rated at 12 volts and 3.78 watts.
The rear side marker position on the Peterbilt 320 uses the 1816 bulb for model years 1987-1997.
The 1816 is an ANSI-standard miniature wedge bulb in the T3.25 form factor, rated at 12 volts and 4 watts.
Although both the 194 and 1816 share the same wedge base style and 12-volt operating voltage, they are not the same bulb. The 1816 carries a slightly higher wattage and occupies a smaller T3.25 envelope compared to the T10 of the 194, making them non-interchangeable.
The T10 designation of the 194 bulb refers to a tubular envelope that is 10 eighths of an inch wide, a standard sizing convention used across ANSI-classified miniature bulbs.
The T3.25 designation of the 1816 bulb follows the same ANSI convention, indicating a tubular envelope 3.25 eighths of an inch wide, which is physically smaller than the T10.
Both bulbs conform to ANSI standards recognized in the United States and Canada, meaning replacements sourced from either market are electrically and physically equivalent within their respective part numbers.