Ford Aerostar Back Up Light Bulb Size

Additional Notes

• The Ford Aerostar backup light specifications span the 1986-1997 model years and reference three distinct bulb types: 1156, 2356, and 2456.
• The 1156 is a single-filament bulb rated at 12V and 21W, fitted with a BA15s bayonet base. It appears in the 1986-1987 Ford Aerostar backup light position.
• The 2356 is a dual-filament bulb operating at 12V and uses a BAY15d bayonet base. The BAY15d base differs from the BA15s in that its two mounting pins are offset at different heights, making it physically incompatible with BA15s sockets.
• The 2456 is a festoon-type bulb rated at 12V, intended for specialty applications. Festoon bulbs are cylindrical in form and mount by contact pressure at each end rather than by a bayonet base, making them mechanically distinct from the 1156 and 2356.
• Because the 1156 uses a BA15s base and the 2356 uses a BAY15d base, these two bulbs are not interchangeable despite both being single-contact and double-contact bayonet types respectively. Substituting one for the other risks improper seating or electrical contact failure.
• The 2456 festoon type is likewise not interchangeable with either the 1156 or the 2356, as its mounting method and physical form are fundamentally different from bayonet-base bulbs.
• All three bulb types listed carry ANSI standard designations valid for both the United States and Canada, indicating conformance to a shared North American specification framework.
• The backup light position on the Aerostar used the 2456 festoon bulb across 1989, 1991, and 1993-1995, while the 2356 dual-filament bayonet bulb was specified for 1988, 1990, 1992, 1996, and 1997.