Ford Fiesta Dome Light Bulb Size

Ford Fiesta dome light bulbs come in 3 distinct sizes: 578, 12961, and 97, with each bulb size corresponding to specific vehicle production years. The replacement chart covers Ford Fiesta models from 1979 through 2019, detailing which bulb size applies to each year range.

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
2019	578
2014-2018	12961
1979-1980	97

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Festoon bulb, 41mm length, end-cap contacts. 12V, 12W.	578
Philips part number. Miniature wedge bulb (T10) with W2.1x9.5d base. 12V, 5W.	12961
ANSI standard (US & Canada). Single-filament bulb with BA15s bayonet base. Variant of 1156. 12V, 13W.	97

Other Locations

Additional Notes

The Ford Fiesta dome light draws from three distinct bulb types across its model years: the 578, the 12961, and the 97.
The 12961 is a Philips part number designation for a T10 miniature wedge bulb with a W2.1x9.5d base, rated at 12V and 5W. It is the specified dome light bulb for the Ford Fiesta across the 2014-2018 model years.
The 578 is an ANSI-standard festoon bulb rated at 12V and 12W, with a 41mm length and end-cap contacts. It is specified for the 2019 Ford Fiesta, and its wattage is notably higher than the 12961 used in prior years.
The festoon form factor of the 578 means it bridges two contact points at either end of the bulb rather than using a socket base, which is a physically distinct mounting method from the wedge base of the 12961.
Because the 578 and 12961 use different base types and wattage ratings, they are not interchangeable between the 2019 and 2014-2018 model years despite both serving the dome light position.
The 97 is an ANSI-standard single-filament bulb with a BA15s bayonet base, rated at 12V and 13W. It is specified for the Ford Fiesta in the 1979-1980 model years.
The 97 bulb is noted as a variant of the 1156, sharing the BA15s bayonet base type, though the two are not identical and substitution between them warrants verification of wattage and fitment compatibility.
The BA15s bayonet base of the 97 is mechanically incompatible with both the wedge base of the 12961 and the end-cap contacts of the 578, making cross-era substitution physically impossible without modification.