Seagrave Fire Apparatus L high beam headlight bulbs measure H4651 in size, while low beam headlight bulbs measure H4652 or H4656 in size. The replacement chart covers vehicle production years spanning 1989 to 2003 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 H4651, H4652, and H4656 bulb types are the three sealed beam units specified across the high beam and low beam headlight positions of the Seagrave Fire Apparatus L.
All three bulb types conform to ANSI standards recognized in both the United States and Canada, and all operate at 12 volts.
Each of these units follows the 4x6-inch rectangular sealed beam format, a standardized form factor in which the lens, reflector, and filament are fused into a single glass envelope rather than housing a separate replaceable bulb.
Because the entire unit is replaced rather than an internal bulb, the H4651, H4652, and H4656 are not interchangeable with bulb-style headlight assemblies.
The high beam headlight position uses the H4651 exclusively across all listed model years, spanning 1989-2003.
The low beam headlight position does not use a single uniform bulb type. The H4656 is specified for the 1989 and 2002 model years, while the H4652 is specified for 1998-1999 and 2001-2003.
The H4652 is classified as a variant of the H4651. Despite their shared physical format and voltage rating, substituting one for the other in the low beam position would not reflect the manufacturer's stated specifications.
The distinction between H4652 and H4656 in the low beam position across different model years of the Seagrave Fire Apparatus L indicates that fitment is year-specific and should not be assumed consistent across the full production range.