Mercury Cyclone high beam headlight bulbs measure H5001 in size, while low beam headlight bulbs measure H5006, with each bulb size corresponding to specific lighting functions. The replacement chart covers vehicle production years spanning 1964 to 1971, detailing bulb specifications across the model's manufacturing period.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mercury Cyclone uses the H5001 sealed beam unit for high beam headlights across all documented model years, spanning 1964-1971.
The H5001 is a 4-inch square sealed beam unit operating at 12V. It conforms to ANSI standards recognized in both the United States and Canada.
The low beam headlight position across the same 1964-1971 span calls for the H5006 sealed beam unit, also rated at 12V and built to the same ANSI standard.
The H5006 is a 5.75-inch round sealed beam unit, making it physically distinct from the square H5001 used in the high beam position. The two units are not interchangeable.
Both the H5001 and H5006 are sealed beam units, meaning the lens, reflector, and filament are fused into a single assembly. When a filament fails, the entire unit requires replacement rather than an internal bulb swap.
The square format of the H5001 and the round format of the H5006 reflect a common practice in sealed beam headlight systems of that era, where beam position and housing shape were standardized together under ANSI specifications.