White WCM Back Up Light Bulb Size

The White WCM back up light utilizes a single 1156 bulb size for the lighting component across all listed vehicle versions. Available information covers a specific time range starting from 1981 through 1988.

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
1981-1988	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 1156 is the sole bulb type specified for the back up light across all listed model years of the White WCM, covering 1981-1988.
The 1156 is an ANSI-standardized bulb recognized in both the United States and Canada, meaning it conforms to a defined set of electrical and physical specifications shared across those markets.
It operates on a 12-volt system and draws 21 watts, which is typical of incandescent automotive bulbs used in signaling and reversing light applications.
The 1156 uses a BA15s bayonet base, a single-contact fitting where the "s" denotes a single pin, distinguishing it from the dual-contact BA15d variant.
As a single-filament bulb, the 1156 serves one dedicated function per socket, which aligns with its role in a back up light rather than a combined stop/tail application.
The BA15s bayonet base requires a quarter-turn locking motion for installation, a mounting style common in commercial and heavy-duty vehicle lighting sockets of that era.
Because the 1156 carries a single filament and a single-contact base, substitution with a dual-filament bulb such as the 1157, which uses a BA15d base, is not compatible with this application.