GMC C6000 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 C6000 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 type rated at 12V and 3.78W, and it appears in both front and rear side marker applications throughout most of the covered 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 types also listed in these specifications.
The 168 is a T10 miniature wedge bulb rated at 12V and 4.9W. Although it shares the same T10 wedge form factor as the 194, its wattage is higher, and the two are listed under separate fitment conditions for the GMC C6000 front side marker in 1983 and 1984.
The 1895 is a T5 miniature wedge bulb rated at 12V and 0.9W, making it the lowest-wattage type in these specifications. It appears exclusively in the rear side marker position for Heavy Duty configurations in 1979 and 1980.
The 168 and 194 share the T10 wedge base form factor, but their wattage ratings differ. Because the specifications list them under distinct fitment conditions rather than as interchangeable options, substituting one for the other is not supported by these fitment data.
For the GMC C6000 front side marker in 1981-1982 and 1989, the 1157 bayonet-base bulb is specified for Medium Duty configurations without the rectangular headlight qualifier, while the 194 wedge bulb is specified for Medium Duty configurations with 2 rectangular headlights. The two bulb types are not interchangeable due to their differing base designs and electrical characteristics.
The 1895 T5 wedge and the 194 T10 wedge are listed as separate fitments for the rear side marker in 1979 and 1980, corresponding to Heavy Duty and Medium Duty configurations respectively. Their different T-size designations indicate physically distinct bulb envelopes, and the specifications do not treat them as interchangeable.
In 1988, the GMC C6000 front side marker carries two separate fitment entries: the 1157 for the standard Medium Duty configuration and the 194 for the Medium Duty configuration with 2 rectangular headlights. The headlight configuration is therefore a determining factor in bulb selection for that year.
All four bulb types listed in these specifications conform to ANSI standards applicable in both the United States and Canada, indicating a standardized electrical and dimensional basis shared across the bulb designations used in this application.