Ford Mustang II Back Up Light Bulb Size

The Ford Mustang II back up light uses a 1156 bulb size for the replacement bulb specification. The chart contains replacement bulb size data covering 1974 to 1978 vehicle production years.

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
1974-1978	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 Ford Mustang II uses the 1156 bulb for the back up light across all listed model years, spanning 1974-1978.
The 1156 is an ANSI-standardized bulb, meaning its physical and electrical specifications are governed by a recognized North American standard applicable in both the US and Canada.
This bulb operates on a 12-volt electrical system and draws 21 watts, which is typical for incandescent reverse lighting applications.
The 1156 is a single-filament bulb, meaning it serves one lighting function only, as opposed to dual-filament types that handle two functions such as braking and running light simultaneously.
It uses a BA15s bayonet base, where "BA15s" denotes a bayonet fitting with a 15mm collar and a single contact pin, which locks into the socket with a push-and-twist motion.
The BA15s single-contact base is not interchangeable with the BA15d base, which carries two contact pins and is found on dual-filament bulbs such as the 1157.