Kovatch Firetruck high beam headlight bulbs use H4651 size while low beam headlight bulbs use H4656 or H4652 size. The replacement chart covers vehicle production years spanning 1988 to 2015 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 are all ANSI-standardized sealed beam units used across the Kovatch Firetruck headlight system. Each operates at 12 volts and follows the 4x6-inch rectangular sealed beam format established under North American ANSI standards applicable in both the United States and Canada.
Sealed beam units of this type house the filament, reflector, and lens within a single fused glass assembly. When the filament fails, the entire unit requires replacement rather than an internal bulb swap, which distinguishes them from composite headlight housings that accept replaceable bulb capsules.
The H4651 is the sole bulb type specified for the high beam headlight position across all model years from 1988 to 2015, indicating a consistent sealed beam fitment for that function throughout the full production range covered by these specifications.
The low beam headlight position uses either the H4652 or H4656 depending on the model year. Both are 4x6-inch rectangular sealed beam units operating at 12 volts, though the H4652 is noted as a variant of the H4651, and the two types are not listed as interchangeable within these specifications.
Because the H4652 is described as a variant of the H4651 rather than an equivalent replacement, substituting one for the other in the low beam position without confirming fitment compatibility carries a risk of incorrect installation, particularly given that beam pattern and wattage can differ between sealed beam variants sharing the same physical housing size.
The low beam specifications for the Kovatch Firetruck show H4656 fitment in 1988, 1990-1991, 1995, 2003, 2005, and 2011, 2013-2015, while H4652 fitment applies to the remaining years within the 1988-2015 range, including 1989, 1992-1994, 1996-2002, 2004, 2006-2010, and 2012.