Jeep CJ5A Back Up Light Bulb Size

The Jeep CJ5A back up light requires a 1156 bulb size for proper illumination. The replacement chart covers vehicle production spanning 1966 to 1968.

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
1966-1968	1156

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

The 1156 is the sole bulb type listed for the Jeep CJ5A backup light across the 1966-1968 model years.
The 1156 is an ANSI-standardized bulb, meaning it conforms to a defined specification recognized across the United States and Canada.
It is a single-filament bulb, which means it serves one lighting function only, as opposed to dual-filament bulbs that handle two functions such as braking and running light from a single unit.
The 1156 uses a BA15s bayonet base, a single-contact mount where the bulb is inserted and twisted to lock into place.
At 12 volts and 21 watts, the 1156 operates on a standard automotive electrical system voltage with a moderate wattage output typical of dedicated backup lighting.
The BA15s base designation indicates a single contact point at the base, which is a fitment-critical detail, as the visually similar BA15d base carries two contact points and is not interchangeable with the BA15s.