Seagrave Fire Apparatus M headlight bulbs utilize H4651 size for high beam and H4656 size for low beam applications. The replacement chart covers 1985 to 1986 production years with corresponding bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The H4651 and H4656 are the two bulb types specified for the Seagrave Fire Apparatus M across the 1985-1986 model years, with the H4651 assigned to the high beam headlight position and the H4656 assigned to the low beam headlight position.
Both the H4651 and H4656 conform to ANSI standards recognized in the United States and Canada, and both take the form of 4x6-inch rectangular sealed beam units operating at 12 volts.
As sealed beam units, neither the H4651 nor the H4656 contains a separately replaceable bulb element. When either unit fails, the entire sealed assembly requires replacement rather than an internal component.
Although the H4651 and H4656 share the same physical format and voltage rating, they are position-specific and are not interchangeable with each other, as each is designated for a distinct beam function.