Plymouth Caravelle high beam headlight bulbs measure H4651 in size, while low beam headlight bulbs measure H4656, with each bulb size corresponding to specific lighting functions. The replacement chart covers 1985 to 1988 production years and details bulb size specifications for each model year.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Plymouth Caravelle uses the H4651 bulb size for the high beam headlight across the 1985-1988 model years.
The low beam headlight position calls for the H4656 across the same 1985-1988 span, making it a distinct unit from the high beam despite sharing the same physical housing format.
Both the H4651 and H4656 are sealed beam units conforming to the ANSI standard recognized in the United States and Canada. In a sealed beam design, the reflector, lens, and filament are fused into a single glass envelope, meaning the entire unit is replaced rather than an internal bulb.
Both units are rated at 12 volts, which is consistent with the standard electrical system voltage found in passenger vehicles of this era.
The H4651 and H4656 share a 4x6-inch rectangular form factor. Although they occupy the same physical space, the two part numbers are not interchangeable, as each is designated for a specific beam function.
The consistent use of H4651 and H4656 across all four model years indicates that Plymouth made no changes to the headlight specification for the Caravelle during the 1985-1988 production run.