according to the parts list, Fordson fitted different bulbs. One for the side mounted lamps and one for the grille mounted lamps. The bulb on the LH side of the picture shows the bulb for grille mounted head lamps (according to the parts book) and the RH side shows the bulb for the side mounted head lamps. The LH bulb has a reflector inside to give low-beam light, but the other has two wires with no reflector. How can I end up with low-beam and high-beam with no reflectors inside?
My first thought was, that the switch powers one wire for low-beam and both wires for hight-beam, but the switch just powers one wire at time. Hmm, seems to be something fishy ... any ideas?
Does the fishy bulb also have two connections on the bottom?
Because the light-intensity is determined by the resistance in the glowing-wire.
Maybe there are two different wires fitted inside.
One way to find out is to use an Ohm-meter.
The connection with the lower resistance would then be the high beam.
Hello Stefan,
I agree with Dunggatherer.
This is typical of the older style of bulbs.
If you look on the side of the bulb, or maybe the box it came in, you will see something like 12V 15/25W. This shows that the bulb has two filaments, one is 15 Watts, the other is 25 Watts power. 'Dipping' the headlight just means swapping to the lower power filament.
There should be two contacts on the bottom of the bulb. They are the '-' contacts for the 15W and the 25W filament. The third contact is the metal casing, which is the '+' contact and 'common' to both filaments.
Just the same on the headlight bulbs for my '56 Major.
You will need to make sure you fit the bulb the correct way. It will fit 180 degrees wrong and this will make the higher power light on low beam, and vice-versa. It's only a case of removing and turning it, if you get it wrong.
On later bulbs, they put the two little pins (called baynets) at different heights, so it would only fit one way.
On very modern bulbs, like the one on the left of your picture, they put a 'notch' or cut out instead.
Mike
Last edited by Mike Kuscher on Tue Jul 29, 2008 10:06 pm, edited 1 time in total.
Dunggatherer,
maybe I bought the wrong bulbs, because they are 12V 35/35 W.
Mike,
your right, the bulb has two "+" terminals, one for each wire and "-" on the housing. The two pins to hold the bulb in the holder are on the same high, so it fits both directions.
If you look closely at your new bulb you will notice that one filament is central and the other is some distance from center. The filament that is central is high beam and the one that is offset is low beam. When corectly installed the fillaments should be horisontal with the low beam filament above the high beam filament (yes I do mean above for low beam). Lights that use those bulbs also have provision for adjusting the bulb in and out for focus as well. When you change bulbs in these types of lights you usually need to adjust the bulb position to get the best beam patern because each bulb is slightly different. However lights with bad reflectors will be hard to adjust as the light will go all over the place and the patern will be hard to pick so I would just put the bulbs in those and hope for the best. These are early non pre-focused bulbs.
The other bulb with the flange and the hat is a pre-focused bulb where the flange on the bulb sets the exact distance to the focus point in it's mating reflector. These are only used in more modern headlights. The non pre-focused bulbs are the ones that my E27N headlights use, but I am not sure which would be right for your dexta.
The theory behind it is simply using a parabolic reflector to form a beam of light. In a good headlight the beam is formed by the reflector and the filament being exactly at the focus. When it is perfect the beam will come out of the light perfectly straight. If the filament is slightly high the reflector will reflect the beam down giving low beam. The glass lens on the front is designed to spread the light sideways but not vertically, otherwise you would end up with two narrow seach light type beams. I hope this helps.
Regards, Frank.
P.S. The early lamps often had the same wattage for high and low beam. The low beam simply pointed lower. Some very early cars used a solenoid to tilt the lights down rather than use two filaments.
The correct globe was a 12 volt 36/36 wattage. Part No. E27N 13007. This suited all side mount headlights from 1946.
Part No. 957E 13007 was a 12 volt 36 main/24 dipped double filament double contact globe and this was used in all centre mount headlights from October 1960.
just to let you know: I assembled the head lamps and gave it a try. It works pretty fine. I don't know why, but it works, the lamps have low-beam and high-beam. Maybe Frank was right with his desciption ....
