Ford Aerostar Parking Light Bulb Size

Additional Notes

• The Ford Aerostar parking light specifications cover model years 1986-1997 and reference six distinct bulb sizes across that span: 1157, 1157NA, 1034NA, 2357, 3157, and 3157NA.
• All six bulb types in these specifications conform to ANSI standards applicable in both the United States and Canada, and all operate at 12 volts.
• Four of the six bulb types use a BAY15d bayonet base: the 1157, 1157NA, 1034NA, and 2357. The remaining two, the 3157 and 3157NA, are T25 wedge-base bulbs.
• The 3157 and 3157NA are electrically identical at 27W/7W, with the only difference being that the 3157NA incorporates natural amber glass. The Ford Aerostar used the 3157 for the 1988-1989 model years and the 3157NA for 1997.
• The 1157 and 1157NA share the same BAY15d base and the same 21W/5W power rating. The 1157NA adds natural amber glass. The Aerostar used the 1157 for 1986-1987, the 1157NA for 1992-1993, and the 1034NA, a variant of the 1157, for 1994-1996.
• The 1034NA is described as a variant of the 1157NA, sharing its BAY15d base and natural amber glass, but rated at 21/5W rather than the 21W/5W of the 1157NA. These two types are not confirmed as interchangeable within these specifications.
• The 2357 is a brighter variant of the 1157, sharing the BAY15d base but rated at 26.9W/8W compared to the 1157's 21W/5W. The Aerostar used the 2357 for the 1990-1991 model years.
• The dual-filament design present in all six bulb types serves two functions within a single housing: the higher-wattage filament typically handles the turn signal or brake function, while the lower-wattage filament handles the parking light function.
• Because the 3157 wedge base and the BAY15d bayonet base are physically incompatible, bulbs specified for 1988-1989 and 1997 cannot be substituted with bulbs specified for other years without a socket adapter or housing modification.
• The 1990-1991 2357 bulb, while physically compatible with BAY15d sockets, draws noticeably more current than the 1157-family bulbs used in adjacent model years, which is a relevant consideration when evaluating cross-year substitution.