Mercury Grand Marquis Turn Signal Bulb Size

Additional Notes

• The Mercury Grand Marquis front turn signal uses one of four bulb families across its production span: the 1034NA, 1157NA/1157, 2357NA, 3157NA, 3357NA, and 3457NA, reflecting several distinct hardware generations over the model's history.
• The "NA" suffix present on most front turn signal bulbs in these specifications denotes natural amber glass, meaning the lens color is built into the glass envelope itself rather than relying solely on an amber housing or lens to produce the required amber signal output.
• The 3457NA is the most frequently specified front turn signal bulb for the Mercury Grand Marquis, appearing across the 1998-2010 model years with the exception of 2002 and 2008, and is a dual-filament T25 wedge type rated at 12V with a 27W high filament and a 7W low filament.
• The 3357NA is a single-filament variant within the same T25 wedge family as the 3457NA, rated at 12V and 27W, and it appears in the front position for the 1996-1997, 2002, 2008, and 2011 model years. Because it lacks a second filament, it is not a drop-in functional replacement for the dual-filament 3457NA despite sharing the same base type.
• The 3157NA and 3457NA share the same T25 wedge base and identical wattage ratings of 27W/7W at 12V, making them physically and electrically similar, though they carry distinct ANSI numbers and are listed as separate fitments in these specifications.
• For the 1988-1990 front turn signal positions, the Mercury Grand Marquis used the 2357NA, a dual-filament bulb with a BAY15d bayonet base rated at 12V, 26.9W/8W. This base type differs from the wedge base used in later model years, making the two families non-interchangeable.
• The 1157NA and its variant the 1034NA both use the BAY15d bayonet base and share a 12V, 21W/5W rating. The 1034NA is described as a variant of the 1157 and appears in the front turn signal position for the 1975, 1977-1978, and 1983 model years, while the 1157NA covers the remaining front positions from 1979-1987 with the exception of 1986.
• The 1986 front turn signal is the only position in these specifications calling for the 1157 without the NA suffix, indicating a clear-glass bulb rather than an amber-glass one, while the rear turn signal for that same year also uses the standard 1157.
• The rear turn signal for the Mercury Grand Marquis used the 1157 from 1975-1986, then transitioned to the 3157 from 1987-2005, and then to the 4157 from 2006-2011. The 3157 and 4157 are both dual-filament T25 wedge bulbs rated at 12V, 27W/7W, though they carry different ANSI designations and are not listed as interchangeable in these specifications.
• Unlike the front turn signal bulbs, none of the rear turn signal bulbs listed for the Mercury Grand Marquis carry the NA suffix, indicating that all rear positions across the full model span rely on clear-glass bulbs rather than natural amber glass envelopes.