Renault R18i Back Up Light Bulb Size

The Renault R18i back up light uses 1156 and P21W bulb sizes for the rear illumination system. Data for the specific components covers the period from 1981 through 1986.

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
1981-1986	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 Renault R18i uses the 1156 bulb across all listed model years, spanning 1981-1986.
The 1156 is an ANSI-standardized bulb type, meaning its physical and electrical specifications are governed by a recognized North American standard used in the United States and Canada.
The 1156 operates on a 12-volt electrical system and draws 21 watts, which is consistent with standard automotive reverse light applications.
The 1156 is a single-filament bulb, meaning it serves only one lighting function, as opposed to dual-filament types that handle two functions such as braking and running lights simultaneously.
The 1156 uses a BA15s bayonet base, where "BA15s" denotes a single-contact bayonet fitting with a 15mm base width, requiring a quarter-turn to lock into the socket.
The BA15s base is not interchangeable with the BA15d base, which is a dual-contact variant of the same bayonet family, and substituting one for the other is not compatible with the Renault R18i's socket design.