The term H1 actually more correctly refers to a type of halogen bulb, but over time in the Porsche world it has come to stand for the headlamp assemblies made by Bosch that use two H1 bulbs. The following information has been gathered from my experience with these fascinating devices and from informative discussions on the Early 911S Registry and other research - and experience restoring them.
Telling the difference between H1’s and H4’s
It’s easy to identify H1’s vs. H4’s when you know what you’re looking for:
History of Bosch H1's
Here are some historic facts in no particular order:
- The first halogen bulb for vehicle headlamp use, the H1, was introduced in 1962 by a European consortium of bulb and headlamp makers.
- Bosch introduced headlights with H1 bulbs in 1966 and headlights with dual filament H4 bulbs in 1971. Strictly speaking that means that H4 headlamps are not correct for SWB cars. Source: Bosch Automotive: A Product History.
- H1’s were first offered as a factory option for the 1968 911S beginning with chassis 11800226 (coupes) and 11850065 (Targas) and additionally for 911T’s and 911E’s starting in 1969 (from posts by Registry members citing Bosch and Porsche publications). They were available as after-market add-ons beginning with their introduction in 1966.
- H1’s didn’t become legal in the U.S. Until 1997 !
- There was one generation, or model, of early H1’s made with city lights in the buckets. These appear to be uncommon.
- The first LHD lenses were marked …007 with raised letters on the outside of the lens and had a larger prism, with two bars on the top of the prism (1966-1969).
- The next generation of LHD lenses were marked …010 with raised letters on the outside of the lens and had a smaller prism with one bar at the top of the prism (1969-1972). There is definitive evidence that the raised script lenses were used at least into 1972. Source: Owner of Porsce Parade Concours Trophy winning 1972 911S.
- The subsequent, and current, generation of LHD lenses are marked …010 with raised letters on the inside of the lens (1973-present)
- H1’s were made for and used on early VW’s. The chrome trim ring has the mounting tab at the 6:00 position and they had the small bulb “city lights”.
- There are two versions of the low beam bulb holders, probably a generational change.
Information on AC Restoration Services for Bosch H1 Headlights