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Difference between H4 & H5
Just wondering what the difference is between the H4 and H5 headlights. I looking to replace the headlights on my 79' 911. Thanks.
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12-28-2000, 09:14 PM
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The H4 bulb has an all-metal base and the lens for the assembly is glass, whereas the H5 has a plastic base bulb and a plastic lens. The H4-type is more durable and can use higher-power bulbs safely.
------------------ Warren Hall 1973 911S Targa |
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12-28-2000, 10:29 PM
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I may be 100% wrong, but as I understood it, the H4s were never made available on Porsches in the USA because of old U.S. laws (since revised) about non-sealed-beam lighting. Because they didn't conform to the laws, the H4s were never submitted for DOT approval. By the time the US laws were revised, Porsche was using H5s. As a result, the H4s were never given DOT approval, and it's not technically legal to use them, although they're the same technology as a lot of other approved lights. They're also generally considered better units than the H5s. H4s are readily available through aftermarket sources, and -- although they're technically for off-road use only -- I've never heard of anyone being cited for them.
------------------ Jack Olsen 1973 911 T (3.6) sunroof coupe |
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12-28-2000, 10:59 PM
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Jack, thats interesting because I know someone who just imported a 89 Carrera Clubsport over from Germany and part of Getting it able to be certified for registration here requried the changing of several lights and lenses,emmisions stuff,ect ect. The conversion place put H-4's on it and that satisfied the headlight requirement.
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12-29-2000, 07:37 AM
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I also want to install H4 lights, but will they plug and work fine or is the H4 circuit different in that it requires a separate ground for the low beam?
Mike 86 Carrera t |
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12-29-2000, 07:59 PM
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Mike,
Yes, they plug into the wiring harness plug just like a sealed beam headlamp bulb. You may want to read the following thread, and install relays, just to ensure the longest possible life from your control stalk and light switch: http://www.pelicanparts.com/ultimate/Forum3/HTML/004536.html ------------------ Warren Hall 1973 911S Targa |
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12-29-2000, 08:12 PM
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Hey, does that mean that the H4s on my 1974 coupe were added on later? What would have been the stock lights?
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12-29-2000, 08:14 PM
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Mike,
I'm glad I led with the "I may be 100% wrong" part, then. 
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12-30-2000, 01:18 AM
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