Article: 74811 of rec.autos.tech
From: wyattk@oissvr.ColumbiaSC.NCR.COM (Kershner Wyatt)
Subject: Re: Can someone explain H3 & H4 bulbs?
Organization: NCR Corp., Columbia SC
Date: Fri, 21 Apr 1995 15:14:41 GMT
Lines: 24

>In article <3mjreh$so2@dove.nist.gov>, keys@starchild.ncsl.nist.gov (Larry Keys) writes:
>> 
>> Would someone please explain the difference between H3 & H4 lighting?
>> 
>
>
>They're different ;-).  The H-3 bulb has one wire coming out of it, also
>the bulb is much smaller than the H-4.  The H-4 bulb has two or three
>prongs, which accepts the headlight wiring harness.  In other words, the
>H-4 is meant to replace headlights and the H-3 would be used for fog or
>driving lights.

Let's add some confusion to this.  There are also H-2 bulbs which are used
in fog and driving lamps and H-1 used in High Beams.

So what we have:

H-1 - high beam bulb, 2 contacts, 60W usually
H-2 - auxilliary lamp bulb, 2 contacts, plugs into a spring socket, usu. 55W
H-3 - auxilliary lamp bulb, socketed, with power wire, usu. 55W
H-4 - Hi/Lo headlamp bulb, 3 prong, various watt. 55W/60 being most common.