Dodge D450 Back Up Light Bulb Size

The Dodge D450 back up light requires 1156 and P21W bulb sizes for the specific lighting components. Available data for the bulb specifications covers the range from 1978 to 1981.

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
1978-1981	1156

Bulb Specifications

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

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Additional Notes

The 1156 is the specified back up light bulb for the Dodge D450 across the 1978-1981 model years.
The 1156 bulb follows the ANSI standard, meaning it conforms to a recognized North American specification used in both 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 lights simultaneously.
The 1156 uses a BA15s bayonet base, a single-contact mount where the bulb is inserted and twisted to lock into place rather than screwed in.
The bulb operates at 12 volts, consistent with the standard electrical system voltage found in conventional passenger and light commercial vehicles of that era.
At 21 watts, the 1156 produces a relatively focused output suitable for a reverse lighting application where short-range illumination behind the vehicle is the primary purpose.
The BA15s base designation indicates a single-contact bayonet fitting with a 15mm base width, a detail relevant when sourcing a physical replacement, as visually similar bulbs may carry a different base contact configuration and would not be interchangeable.