Ford Mustang Map Light Bulb Size

Additional Notes

• The Ford Mustang map light bulb specifications span model years 1964 through 2023, with a total of nine distinct bulb sizes used across that period.
• The 12961 is a Philips-designated miniature wedge bulb in the T10 form factor with a W2.1x9.5d base, rated at 12V and 5W. The Ford Mustang uses this bulb for the map light across the 2015-2023 model years, making it the most consistently applied size in these specifications.
• The T10 wedge form factor is the most recurrent across these specifications, represented by bulb sizes 12961, 192, 168, and 906. While all four share the same physical form factor, their wattage ratings differ, ranging from 3W for the 192 to 8W for the 906, which means they are not interchangeable without accounting for those electrical differences.
• The 631 is a single-filament bulb with a BA15s bayonet base, rated at 12V and 21W, and is listed as a variant of the 1156. The Mustang map light used this bulb across the 1964-1968 model years.
• The 1004 is a dual-filament bulb with a BAY15d bayonet base, rated at 12V with a 21/5W dual-filament output, and is listed as a variant of the 1157. Its dual-filament construction distinguishes it from the single-filament 631 and 105 types also present in these specifications.
• The 105 is a single-filament bulb with a BA15s bayonet base, rated at 12V and 13W, and is listed as a variant of the 1156. Although the 105 and 631 share the same BA15s base type, their wattage ratings of 13W and 21W respectively indicate they are not rated equivalents.
• The 212-2 is a festoon bulb with an SV8.5 base, measuring 41mm in length and rated at 12V and 12W. Festoon bulbs differ structurally from wedge and bayonet types, as they are held in place by contact pressure at each end rather than by a base socket.
• The 912 is a T15 wedge bulb rated at 12V and 12W, listed as a variant of the 921. The T15 form factor is physically larger than the T10, so the 912 is not a drop-in substitute for the T10-based bulbs also present in these specifications.
• The 1816 is a miniature wedge bulb in the T3.25 form factor, rated at 12V and 4W. The T3.25 is a narrower form factor than the T10, and the two are not physically interchangeable.
• Bayonet-base bulbs such as the 631, 105, and 1004 require a socket designed for that base type, while wedge and festoon bulbs use entirely different retention mechanisms, meaning base-type compatibility is a necessary consideration when referencing these specifications.