Fiat 131 high beam headlight bulbs use H5001 size while low beam headlight bulbs use H5006 size. The replacement chart covers 1975 to 1978 vehicle production years with corresponding bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Fiat 131 used the H5001 bulb size for high beam headlights across the 1975-1978 model years.
The H5001 is a 4-inch square sealed beam unit operating at 12V. Because it is a sealed beam design, the entire unit is replaced rather than an internal bulb.
The Fiat 131 used the H5006 bulb size for low beam headlights across the 1975-1978 model years.
The H5006 is a 5.75-inch round sealed beam unit also operating at 12V, and it likewise requires full unit replacement rather than individual bulb replacement.
Both the H5001 and H5006 conform to ANSI standards applicable in the United States and Canada, meaning they follow a regulated specification for output and fitment within those markets.
The H5001 and H5006 are physically distinct units. The H5001 is square while the H5006 is round, and their sizes differ, making the two non-interchangeable between high and low beam positions.