Mercury Custom front and rear turn signal bulbs utilize 1034 and 1154 size specifications. The replacement chart covers 1952 through 1956 vehicle production years.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 1154 bulb is the most frequently specified type across the Mercury Custom's turn signal applications, covering both front and rear positions for the 1952-1955 model years.
The 1034 bulb appears in both the front and rear turn signal positions for the 1956 Mercury Custom, replacing the 1154 used in prior years.
Both the 1034 and 1154 are ANSI-standardized bulbs recognized in the US and Canadian markets, and both use the BAY15d bayonet base, a two-pin offset base designed to prevent incorrect insertion.
Both bulb types carry dual-filament construction, meaning each bulb serves two lighting functions within a single housing, which is typical for combined stop and turn signal applications.
The 1034 and 1154 are described as variants of the 1157, a widely used dual-filament automotive bulb, indicating a shared design lineage and base compatibility with BAY15d sockets.
The 1034 is rated at 12V with a 21/5W output, where the two wattage values correspond to its high and low filaments respectively.
The 1154 is rated for operation at either 6V or 12V, reflecting its origin in an era when automotive electrical systems were transitioning between those two voltages.
Despite sharing the same BAY15d base, the 1034 and 1154 are not confirmed as interchangeable, as differences in voltage rating and wattage output between the two types can affect compatibility with a vehicle's electrical system and flasher unit.