Mercury Grand Marquis Dome Light Bulb Size

Additional Notes

• The Mercury Grand Marquis dome light uses the 906 bulb across the majority of its model years, spanning 1980-1984, 1987-1990, and 1992-2011, making it the most consistently specified bulb type in these fitment records.
• The 906 is a T10 miniature wedge bulb rated at 12V and 8W under the ANSI standard applicable in both the United States and Canada. Its wedge base design means it is held in place by the socket itself rather than by a separate locking mechanism.
• The 912 bulb, specified for the Mercury Grand Marquis in 1982, 1985, and 1989, is a T15 wedge bulb rated at 12V and 12W. It is described as a variant of the 921, meaning the two share a physical and electrical relationship but are not identical replacements.
• The 105 bulb, used in 1981 and 1986, carries a BA15s bayonet base and is rated at 12V and 13W. It is described as a variant of the 1156, so the two are related but not interchangeable without verification of the specific socket and wattage tolerance.
• The 1003 bulb, specified for 1977-1978, also uses a BA15s bayonet base but is rated at a notably higher 12V and 21W output compared to the 105. Despite sharing the same base type, the significant wattage difference between the two makes substitution between them a relevant fitment consideration.
• The 211-2 festoon bulb, used in 1975-1976 and 1979, has a 41mm length and an SV8.5 base, rated at 12V and 12W. Festoon bulbs make contact at both ends rather than through a base socket, which distinguishes their installation from wedge or bayonet-type bulbs.
• The 561 festoon bulb, specified for the 1991 Mercury Grand Marquis, is 44mm in length with end-cap contacts, rated at 12V and 12W. Its 44mm length differs from the 41mm of the 211-2, and the two festoon types are not interchangeable due to this physical difference.
• The 1991 model year stands as the only year in the entire span of these records to specify the 561 bulb, isolating it as a unique fitment within the Grand Marquis dome light history.
• All bulb types listed across these specifications conform to ANSI standards recognized in both the United States and Canada, indicating a consistent regulatory framework across the full range of model years covered.
• The transition from the higher-wattage 1003 bulb in 1977-1978 to the lower-wattage 211-2 in 1979 and then to the 906 in 1980 reflects a shift across three different bulb families within a short span, each with a distinct base type and wattage rating.