Ford Prefect front and rear turn signal bulbs utilize 1034 or 1154 size specifications. The replacement chart covers 1950 through 1957 production years with corresponding bulb size data.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Ford Prefect turn signal specifications cover model years 1950-1957, with both front and rear positions using identical bulb sizes in each respective year.
The 1154 bulb is the most frequently specified type across these years, appearing in both front and rear turn signal positions for the 1950-1955 model years.
The 1154 is an ANSI-standard dual-filament bulb fitted with a BAY15d bayonet base, rated for either 6V or 12V operation, and is noted as an older variant of the 1157.
The 1034 bulb replaced the 1154 in both front and rear turn signal positions for the 1956-1957 Ford Prefect.
The 1034 is also an ANSI-standard dual-filament bulb with a BAY15d bayonet base, though it is rated specifically at 12V with a 21/5W output and is described as a variant of the 1157.
Both the 1034 and 1154 share the BAY15d bayonet base, meaning the physical mounting interface is the same across all specified model years.
Despite sharing the same base type, the 1034 and 1154 are not directly interchangeable due to their differing voltage ratings, as substituting a 12V-only 1034 into a 6V system could affect bulb performance and longevity.
The dual-filament construction of both bulb types indicates that a single bulb serves two functions within the turn signal circuit, typically combining a higher-intensity flash filament with a lower-intensity running or parking filament.