Plymouth Conquest Back Up Light Bulb Size

The Plymouth Conquest back up light requires bulb size 1156 or P21W depending on the specific version of the vehicle. Data for the bulb sizes covers the range from 1984 to 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
1984-1986	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 1156 is the sole bulb type listed for the Plymouth Conquest backup light across the 1984-1986 model years.
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 standards shared across those markets.
It is a single-filament bulb, which is typical for backup lights since the function requires only one consistent output state rather than variable brightness levels.
The 1156 uses a BA15s bayonet base, a single-contact mount where the bulb is inserted and twisted to lock into place. The "s" in BA15s denotes a single contact point at the base, distinguishing it from the dual-contact BA15d variant.
The bulb operates at 12 volts and 21 watts, consistent with standard 12V automotive electrical systems.
Because the BA15s base has only one contact pin, it is not interchangeable with dual-contact bayonet bulbs such as the 1157, despite the physical similarity of the socket housing in some vehicles.