Ford Aerostar Brake Bulb Size

The Ford Aerostar brake light utilizes 3457, 2357, and 1157 bulb sizes depending on the specific version of the vehicle. Data for the provided specifications covers the range from 1986 to 1997.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Brake

If US Type and EU Type show the same value, a direct cross-reference for this bulb is not available or the data is insufficient.

Years	US Type	EU Type	Shop
1997	3457	3457	Check Price
1990-1996	2357	2357	Check Price
1986-1989	1157	P21/5W	Check Price

Center High Mount Stop Light

Years	US Type	EU Type	Shop
1994-1997	921	W16W	Check Price

Bulb Specifications

Description	Type	Shop
ANSI standard (US & Canada). Dual-filament wedge bulb (T25). 12V, 27W/7W.	3457	Check Price
ANSI standard (US & Canada). Dual-filament bulb with BAY15d bayonet base. Brighter variant of 1157. 12V, 26.9W/8W.	2357	Check Price
ANSI standard (US & Canada). Dual-filament bulb with BAY15d bayonet base. 12V, 21W/5W.	1157	Check Price
ECE standard (Europe & worldwide). Dual-filament signalling bulb with BAY15d bayonet base. 12V, 21W/5W.	P21/5W	Check Price
ANSI standard (US & Canada). Wedge bulb (T15). 12V, 16W.	921	Check Price

Other Locations

Additional Notes

The Ford Aerostar brake light specifications reference four distinct bulb types across its production years: the 3457, 2357, 1157, and 921.
The 1157 and 2357 bulbs share the same BAY15d bayonet base, which is a dual-contact offset-pin fitting. This base design physically allows one to seat in the socket of the other, creating a fitment risk despite the two types carrying different wattage ratings.
The 2357 operates at 26.9W on its high-intensity filament, while the 1157 operates at 21W on its equivalent filament. Both run on a 12V circuit, but substituting one for the other alters the light output delivered to the brake circuit.
The Ford Aerostar used the 1157 for brake lighting from 1986-1989, then transitioned to the 2357 from 1990-1996, and used the 3457 in 1997.
The 3457 is a T25 wedge-base bulb, which uses a plastic wedge fitting rather than a bayonet base. It is not interchangeable with the 1157 or 2357 despite sharing a dual-filament design and 12V rating.
The 3457 carries a 27W/7W dual-filament rating, placing its high-intensity filament output close to that of the 2357 at 26.9W/8W, though the two bulbs use physically incompatible bases.
The 921 is a single-filament T15 wedge bulb rated at 16W on a 12V circuit. Its single-filament construction distinguishes it from the dual-filament brake bulbs used in the main stop light positions.
The 921 was specified for the Center High Mount Stop Light on the Ford Aerostar for the 1994-1997 model years. This position serves a supplemental braking signal function separate from the primary brake light assembly.
All four bulb types in these specifications conform to ANSI standards recognized in both the United States and Canada, indicating standardized electrical and photometric performance requirements for each type.
The dual-filament design of the 1157, 2357, and 3457 allows a single bulb to serve both a low-wattage running light function and a high-wattage brake or turn signal function within the same housing.