GMC C3500HD front and rear side marker bulbs utilize 194 and 1157 bulb sizes, with front markers accommodating both sizes and rear markers using the 194 size. The replacement chart covers vehicle production spanning 1991 to 2002.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 194 bulb is the most widely used size across the GMC C3500HD side marker specifications, appearing in both front and rear positions across the majority of model years covered.
The 194 is a T10 miniature wedge bulb rated at 12V and 3.78W, conforming to ANSI standards applicable in both the United States and Canada.
The 1157 bulb is a dual-filament type with a BAY15d bayonet base, rated at 12V with a 21W/5W output, and also conforms to ANSI standards for the US and Canadian markets.
The BAY15d bayonet base of the 1157 is physically and electrically incompatible with the wedge socket used by the 194, meaning the two bulb types are not interchangeable.
The GMC C3500HD front side marker for the 1993-2002 model years uses the 194 bulb without any trim or duty designation noted.
The 1992 front side marker on the C3500HD carries a Medium Duty designation and uses the 1157 bulb, which differs from every other model year in the front side marker specifications.
The 1991 front side marker also carries a Medium Duty designation but uses the 194 bulb, not the 1157 used in the 1992 Medium Duty front position.
The rear side marker for the 1991-1992 C3500HD carries a Medium Duty designation and uses the 194 bulb in both years.
The rear side marker specifications for 1993-2002 list the 194 bulb without any duty designation, consistent with the front side marker entries for the same period.
The 2000 model year is present in the front side marker specifications but absent from the rear side marker specifications, with no rear side marker entry recorded for that year.