The Mazda B1800 uses an H5001 bulb size for high beam headlights and an H5006 bulb size for low beam headlights. The replacement chart covers vehicle production years spanning 1977 to 1978.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The H5001 and H5006 are sealed beam units, meaning the lens, reflector, and filament are fused into a single assembly. When the filament fails, the entire unit requires replacement rather than an internal bulb swap.
The H5001 is a 4-inch square sealed beam unit operating at 12V, conforming to ANSI standards applicable in the United States and Canada. It serves as the high beam headlight on the Mazda B1800 for the 1977-1978 model years.
The H5006 is a 5.75-inch round sealed beam unit, also rated at 12V and built to the same ANSI standard. It fills the low beam position across the same 1977-1978 model year range.
The square format of the H5001 and the round format of the H5006 are physically distinct, and the two units are not interchangeable with each other despite sharing the same voltage rating and regulatory standard.
ANSI-standardized sealed beam types such as the H5001 and H5006 were designed to allow cross-brand fitment, meaning units from different manufacturers conforming to the same ANSI designation are generally compatible with the same housing.
Both the H5001 and H5006 carry a 12V rating, which aligns with the standard 12-volt electrical systems used in passenger vehicles of that era.