White/GMC WCA Back Up Light Bulb Size

The White/GMC WCA back up light requires a bulb size of 1156 for the rear illumination system. Data for the specified component covers the period from 1988 through 1995.

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
1988-1995	1156

Bulb Specifications

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

Other Locations

Additional Notes

The White/GMC WCA uses the 1156 bulb for its back up light across all listed model years, spanning 1988-1995.
The 1156 is an ANSI-standardized bulb type, meaning its physical and electrical specifications are defined by a recognized North American standard applicable in both the United States and Canada.
This bulb operates on a 12-volt electrical system and draws 21 watts, which is typical of incandescent automotive reverse lighting applications.
The 1156 is a single-filament bulb, meaning it serves one lighting function only, as opposed to dual-filament types that handle two functions such as braking and running light simultaneously.
It uses a BA15s bayonet base, where "BA15" refers to the 15mm base width and "s" denotes a single contact pin, distinguishing it from the BA15d, which carries two offset pins for dual-filament use.
The single-contact BA15s base is not interchangeable with the BA15d base; substituting one for the other is not possible without modification due to the differing pin configurations.