GMC C15 Back Up Light Bulb Size

GMC C15 back up light bulb size specifications include 1156 and 199 bulb options for this vehicle model. The replacement chart covers vehicle production years spanning 1973 to 1978 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.

Bulb Size by Year Range

Years	Bulb Size
1977-1978	1156
1976	199
1974-1975	1156
1973	199

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. 12V, 21W.	1156
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. Variant of 1156. 12V, 21W.	199

Other Locations

Additional Notes

The GMC C15 back up light specifications cover model years 1973-1978, with two distinct bulb types used across that span: the 1156 and the 199.
The 1156 is the more frequently specified bulb, appearing in the GMC C15 for model years 1974-1975 and 1977-1978.
The 199 bulb is specified for model years 1973 and 1976, making it the less common of the two types across this vehicle's fitment data.
Both the 1156 and 199 are ANSI-standard bulbs recognized in the US and Canada, each operating at 12 volts with a 21-watt output.
Both bulbs use a BA15s bayonet base, which is a single-contact bayonet mount with a 15mm base width, and both are single-filament designs.
The 199 is classified as a variant of the 1156, meaning the two share the same base type, voltage, and wattage ratings.
Despite their technical similarities, the 1156 and 199 carry separate ANSI designations, and fitment data for the C15 treats them as distinct part numbers depending on the model year.