GMC C5000 front and rear side marker bulbs utilize 194, 1157, 168, and 1895 bulb sizes depending on location and model variation. The replacement chart covers 1979 to 1990 production years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The GMC C5000 front and rear side marker positions draw from four distinct ANSI-standard bulb types across the 1979-1990 model range: the 194, 168, 1157, and 1895.
The 194 is the most frequently specified bulb across both positions. It is a T10 miniature wedge bulb rated at 12V and 3.78W, and it appears in front and rear side marker applications across multiple model years.
The 1157 is a dual-filament bulb with a BAY15d bayonet base, rated at 12V with filaments drawing 21W and 5W respectively. Its dual-filament design distinguishes it electrically from the single-filament wedge bulbs also present in these specifications.
The 168 shares the T10 wedge form factor with the 194 but draws 4.9W rather than 3.78W. Although both are physically similar, the wattage difference means they are not electrically identical.
The 1895 is a T5 miniature wedge bulb rated at 12V and 0.9W, making it the lowest-wattage bulb in these specifications. It is specified only for the rear side marker on the 1980 GMC C5000.
On the GMC C5000, the front side marker position for 1981-1985 and 1987-1989 carries two separate bulb size entries per year, with the 194 applying specifically to configurations with 2 rectangular headlights and the 1157 applying to the general Medium Duty designation.
The rectangular headlight configuration note is exclusive to the front side marker position. No equivalent conditional fitment note appears in the rear side marker specifications.
The 1157 bayonet-base bulb and the 194 wedge bulb use physically incompatible mounting systems, so the two types are not interchangeable regardless of voltage compatibility.
For the 1986 front side marker, only a single 194 entry exists without a Medium Duty qualifier, while the 1986 rear side marker specifies the 1157 under a Medium Duty designation, meaning the front and rear positions require different bulb types that year.
The 168 appears only once across all entries, specified for the 1983 front side marker under the general Medium Duty designation, while the 194 is listed separately for the same year under the rectangular headlight configuration.