The Mercury Topaz brake light requires bulb size 2357 or 1157 depending on the specific version. Data for the bulb sizes covers the range from 1984 to 1988.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mercury Topaz brake light circuit uses two bulb types across its production run: the dual-filament BAY15d bayonet base format for the main brake lights, and the single-filament T15 wedge format for the center high mount stop light.
The 2357 bulb, fitted to the Mercury Topaz brake lights for 1986-1988, is a dual-filament ANSI-standard unit rated at 12V with a high-filament draw of 26.9W and a low-filament draw of 8W, using a BAY15d bayonet base.
The 1157 bulb, used in the 1984-1985 model years, shares the same BAY15d bayonet base as the 2357 but operates at lower wattage, rated at 21W on the high filament and 5W on the low filament.
Because the 2357 and 1157 share the BAY15d bayonet base, they are physically interchangeable in the socket, though their wattage outputs differ. The 2357 produces a noticeably brighter high-filament output than the 1157.
The center high mount stop light on the Mercury Topaz used the 912 bulb for 1986-1989 and transitioned to the 921 bulb for 1990-1994.
Both the 912 and 921 are T15 wedge bulbs operating at 12V. The 921 is rated at 16W, while the 912 is rated at 12W, making the 921 the higher-output variant of the two.
The 912 and 921 share the same T15 wedge form factor, which means they are physically compatible with the same socket, though their wattage ratings are not identical.
All four bulb types listed in these specifications, the 2357, 1157, 921, and 912, conform to ANSI standards applicable in both the United States and Canada.