1916 headlight issue

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Jon
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1916 headlight issue

Post by Jon » Sat Mar 21, 2020 12:37 pm

1916 Model T with headlights wired in series, powered by magneto (original set up).
Switch on, right light on, left light off. Removed sockets from headlight assemblies and both lights on. What's happening is the right headlight assembly is grounding. Removed headlight assembly and can find NO way to insulate assembly from grounding. How was this accomplished?

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TMiller6
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Re: 1916 headlight issue

Post by TMiller6 » Sat Mar 21, 2020 12:56 pm

You have the wrong bulb. The correct magneto headlight bulb will only have continuity across the two contacts on the base.
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Steve Jelf
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Re: 1916 headlight issue

Post by Steve Jelf » Sat Mar 21, 2020 2:29 pm

IMG_4990 copy.JPG
Even pins, two contacts. These are pretty common at swap meets. They're not specifically for mag lights, but they work. Despite being marked 6-8V they last pretty well for me. A problem with bulbs a hundred years old is that sometimes when you put them into the socket and try to twist them into position the glass turns and the base doesn't and the bulb is wrecked. I put glue around the seam to prevent that, but I haven't found out yet if it works.

WARNING: The "Magneto Bulb" I bought from one of the parts dealers to try out a few years ago turned out to be rated at 24V. I understand the idea of that is to prevent them burning out, but they're also too dim to light your way. A real magneto bulb is not great, but the 24V bulb is hopeless.


I will drive by mag light in town where there are street lights to help out, but an unfamiliar country road on a dark night is just too scary and dangerous. Voice of experience.
The inevitable often happens.
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old_charley
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Re: 1916 headlight issue

Post by old_charley » Sat Mar 21, 2020 3:34 pm

My '22 was originally a no starter/generator car. I ran with the mag lights for years until I decided to install a generator for the better lights. I also had a problem burning out bulbs occasionally as my magneto was putting out close to 30 volts. It's a nuisance when wired in series. One bulb goes out and you have no lights. I found the following solution that worked somewhat better. I got bulbs from Napa, part # T1683. They are single contact, self grounding. They have two filaments to handle the 28 volts. I changed the lamp sockets to single contact and wired the headlamps in parallel. They give off plenty of light when the engine revs up but are as dull as matches at idle. There's just no way around that with magneto lights.
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Re: 1916 headlight issue

Post by Jeff Hood » Sat Mar 21, 2020 4:15 pm

I suspect that you either have the wrong bulb or a bad socket. A standard 6V or 12V bulb grounds the filaments through the base. A magneto bulb is not grounded through the base, the filament is connected to the two contacts only. Old sockets often have had the little springs between the thimble contacts and the bulb contacts overheated and may have lost their "spring" and may be touching the side of the socket and grounding.


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Jon
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Re: 1916 headlight issue

Post by Jon » Sat Mar 21, 2020 5:53 pm

Guys;
I have removed the sockets from the headlight assemblies, inserted the magneto bulbs from Lang's,(double filament, double contact, straight pins into the sockets with wires attached (in series) and everything works normally, both bulbs light and change intensity with engine rpm.
When I put the sockets back in the headlight assemblies, the right light works and the left one does not. this is not what the series wiring should do.
The only explanation that I have come up with is the right socket is grounding through the headlight assembly. I have switched bulbs, switched sockets, every which way with same result. How can I keep right socket from grounding through headlight assembly? The only thing I have not tried is switching headlight assemblies. There has to be something in the socket holder in the headlight assembly that prevents current to ground, but I can't figure out how it does it.

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Re: 1916 headlight issue

Post by TMiller6 » Sat Mar 21, 2020 6:49 pm

What you are describing is exactly what happens when you put a battery type headlight bulb into a magneto wired socket. If you have an ohmmeter, you will find continuity between either solder button on the bottom and the brass shell of the bulb.

When the sockets are out of the car, the current goes through one filament of the right hand bulb. Finding no ground, then it goes through the other filament through the radiator jumper wire to the other correct magneto bulb.

When you put the sockets back in the car, you satisfy the right hand ground and the left bulb which has more resistance than the ground fails to light.

As in post #1, I maintain you have the wrong bulb.
Last edited by TMiller6 on Sat Mar 21, 2020 6:53 pm, edited 1 time in total.
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Re: 1916 headlight issue

Post by Wayne Sheldon » Sat Mar 21, 2020 7:32 pm

I suspect that the bulbs you have gotten are still not the right ones. The proper magneto bulbs for for the model T MUST have two pin contacts! And neither contact can have continuity to the base. They should NOT have two filaments, but that is possible (depending on how the bulb is wired internally). Check that. Common type (available in several voltage ranges) two contact pins with two filament bulbs will ground both filaments through the bulb base. I would not be surprised if the bulb suppliers have substituted the wrong bulbs because they are marketing, not engineering. (Used to run into that problem at work a LOT!)

I can't be sure without running some tests up close and personal? But what I suspect may be happening.
You have two filament bulbs grounding through the base. When the sockets are in the lamps, the first bulb grounds the first filament through the base. It lights, one filament (you probably can't see that because it is bright and can hurt the eyes), and grounds out through the base and lamp. That grounding in effect shorts the circuit, causing the second lamp to not work.
When you remove the sockets from the lamp, the base isn't grounded now. What happens is that the current flows into the first socket, through one pin connector, through one filament into the base which is now NOT grounded. So the current then flows back from the base through the second filament and on out though the second pin connector. From there to the other socket with the other bulb. If you connect your test ground to the base of the socket. it will take the power in through the first pin connector into the first filament and light it up before heading out through the base ground. If you connect (or keep connected) the second lamp to ground from one of the pin connectors as original wiring dictates? Then the power would again double back through the bulb through the second filament and light both filaments before exiting out through the second pin connector to ground.
Got all that? (Electricity is FUN!)

If I were up close and had my meter? I would run simple tests with my Volt/Ohm meter. But a couple simple things you can do. IF (that big if again) you are grounding the second bulb through the wiring (NOT the base of the bulb), take a wire, and short the ground to the base of the socket/bulb to see it the brightness changes. Also, take that wire, and short the socket/base of the other bulb and see if it changes. Depending upon polarity of connections, shorting the base of the bulb/socket to ground on either bulb may change brightness or turn off the other bulb. Such changes would be a good indication that you have the wrong type of bulbs.
IF (that big if again) however, you were grounding your test with the ground wire attached to the base of the second bulb? The test will be a bit less revealing. Still, any such changes in brightness would still be an indication of the wrong bulbs. You can have the lights on (even with the engine running), and short the bulb base/socket to ground on either bulb (one at a time), and any change in brightness would indicate (but not definitely) that you have the wrong type of bulbs.

(I hope I got all that right, didn't have time right now to proofread it all?)


Topic author
Jon
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Re: 1916 headlight issue

Post by Jon » Sun Mar 22, 2020 12:12 pm

I feel really stupid. I bought two sets of bulbs from Lang's. One set magneto and one set 12V. They arrived unmarked. I assumed the ones with the double filaments were the magneto bulbs as they were most similar to my current magneto bulbs. I was wrong, and all of you that stated I had the incorrect bulbs were absolutely correct. I switched to the other set of bulbs and everything worked properly. Thanks to all of you that responded, I will listen more intently from now on.

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Steve Jelf
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Re: 1916 headlight issue

Post by Steve Jelf » Sun Mar 22, 2020 1:23 pm

I switched to the other set of bulbs and everything worked properly.

Have you tried driving with them at night? :)
The inevitable often happens.
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Topic author
Jon
Posts: 11
Joined: Mon Feb 10, 2020 2:37 pm
First Name: jon
Last Name: ewing
* REQUIRED* Type and Year of Model Ts owned: 1915 Model T touring
Location: miami, FL
MTFCA Number: 50886

Re: 1916 headlight issue

Post by Jon » Mon Mar 23, 2020 12:37 pm

I don't intend to drive at night, but if I do it will probably be in city areas with ample ambient light. I felt like the lights were very dim even with about 1500 rpm. However, I do like to have everything working as original on my very original 1916. of course I could always light up my kerosene side lamps HAHA.

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Steve Jelf
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Re: 1916 headlight issue

Post by Steve Jelf » Mon Mar 23, 2020 1:10 pm

I don't intend to drive at night, but if I do it will probably be in city areas with ample ambient light.

That's my policy. To make mag lights become almost adequate you have to go fast enough to outrun them. :D
The inevitable often happens.
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Re: 1916 headlight issue

Post by YellowTRacer » Tue Mar 24, 2020 5:29 pm

I ran bulb #1009 for 30 years, many times driving across the San Francisco Oakland Bay bridge, dark going both ways. Plenty of light above 20 MPH. I tried a couple of other bulbs before I found the 1009s and they would burn out at speed the 1009s never burnt out in 30 years of occasional use.

Ed aka #4

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