Plymouth Trailduster Back Up Light Bulb Size

The Plymouth Trailduster back up light requires bulb size 1156 or P21W depending on the specific configuration of the vehicle. Available data covers the range from 1974 through 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
1974-1981	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 back up light bulb size listed for the Plymouth Trailduster across the 1974-1981 model years.
The 1156 is an ANSI-standardized bulb type, meaning its physical and electrical specifications are governed by a recognized North American standard shared across the United States and Canada.
The 1156 operates on a 12-volt electrical system and draws 21 watts, which is typical of incandescent automotive bulbs used in backup light applications during this era.
The 1156 uses a BA15s bayonet base, a single-contact mount where the "s" denotes a single pin, distinguishing it from double-contact bayonet variants.
Because the 1156 is a single-filament bulb, it serves one lighting function only, which is consistent with its role as a dedicated back up light rather than a combined stop or tail light unit.
The BA15s base type is not interchangeable with the BA15d base, which carries two contact pins. Substituting a double-contact bulb in a single-contact socket is not electrically compatible.
The 1156 is sometimes marketed under the trade designation 7506 in certain international markets, though the ANSI 1156 designation applies to the Plymouth Trailduster specification as listed.