Mercury Grand Marquis Headlight Bulb Size

Additional Notes

• The Mercury Grand Marquis used three distinct headlight technologies across its production span: sealed beam units in earlier model years, followed by single-filament halogen bulbs, and later dual-filament halogen bulbs capable of handling both high and low beam functions within a single housing.
• The 9008 bulb, fitted to the Mercury Grand Marquis for the 2006-2011 model years on both high and low beam positions, is a dual-filament halogen type with a P26t base, rated at 12V and drawing 65W on high beam and 55W on low beam. Its dual-filament design allows a single bulb to serve both functions.
• The 9007 bulb, used across the 1998-2005 model years for both beam positions, shares the same 12V, 65W/55W dual-filament configuration as the 9008 but uses a PX29t base rather than a P26t base, making the two types physically non-interchangeable despite their similar electrical ratings.
• For the 1992-1997 model years, the Grand Marquis used separate single-filament bulbs for each beam function: the 9005 (P20d base, 65W) for high beam and the 9006 (P22d base, 55W) for low beam. Although these bulbs share a similar physical profile, their base types differ, and they are not interchangeable between positions.
• The H4651 and H4656 sealed beam units, used across various model years from 1979-1991, are both 4x6-inch rectangular sealed beam formats operating at 12V. Because the lens, reflector, and filament are fused into a single glass unit, the entire assembly requires replacement rather than just an internal bulb.
• The H4652 sealed beam unit, specified for the low beam position in the 1983 and 1988-1989 model years, is a variant of the H4651 format within the same 4x6-inch rectangular sealed beam family, also requiring full unit replacement at 12V.
• The 1975-1978 model years used round sealed beam units: the H5001 for high beam, a 4-inch square sealed beam, and the H5006 for low beam, a 5.75-inch round sealed beam. Both operate at 12V and require full unit replacement, and their differing physical formats mean they are not interchangeable with each other or with the rectangular sealed beam types used in later years.
• All bulb and sealed beam types specified for the Mercury Grand Marquis across all listed model years conform to ANSI standards applicable to the US and Canadian markets, and all operate on a 12V electrical system.