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Headlight bulb non-starter

Posted: Wed Oct 16, 2019 3:57 pm
by john in kzoo
Quick question, I used the replacement bulb listed in one of the supplier's catalogs to replace my headlight bulbs ('15 touring non-starter). The bulb was the one specified for magneto use, anyway upon installation the light is exceptionally dim. I think I should try a 12 volt bulb...

Re: Headlight bulb non-starter

Posted: Wed Oct 16, 2019 4:28 pm
by Scott_Conger

yours is a common question...Google "MTFCA Magneto bulb" and see the results.

Our '15 starts easily on mag, yet because of bulb problems and varying voltages when on MAG, I took the opportunity to use the (incorrect) battery carrier that was in the car and have rigged 12V bulbs to run off the battery. I also installed battery tender wires to the battery that exit the car at a convenient location to do an occasional recharge. Limited light use leads to very little draw-down and the tender makes up for it just fine. It also gives very bright lights. The battery is not obvious and the battery tender plug is inconspicuously located in the engine compartment, so simply lifting the driver's side hood and plugging in overnight every couple of months takes care of things. The installation of the bulbs is in parallel, so I can suffer a failure without losing both bulbs and the overall effect of the installation is almost invisible.

Re: Headlight bulb non-starter

Posted: Wed Oct 16, 2019 5:57 pm
by Steve Jelf
The "Magneto bulb" available from the parts dealers isn't. I bought one to try, and found that it was actually a 24v bulb. Even with the magneto running fast, that's inadequate. I assume the idea is that it will last. I dare say it will, and it will also be useless. Lighting even with proper mag bulbs is marginal at best. If I remember correctly those are rated at 9 volts, so a 24 volt bulb is ridiculously dim.

As far as I know, there are no new magneto bulbs. I buy old ones at swap meets and auctions. Some of the bulbs I use are labeled 6-8 volts. They last surprisingly well. They will burn out eventually, but I get quite a bit of driving out of them. A problem some old bulbs have is dried out shellac that lets go of the glass when you try to twist the bulb in the socket, so the bulb is wrecked. The ones I'm currently using are OK, but I intend to make it a winter project to add new glue to a dozen or so.

I find magneto lights adequate for driving in town, which is so well lit that you could really drive without headlights, and on a familiar country road coming home. But having had the experience, I will not depend on mag lights on an unfamiliar country road.

IMG_2981 copy.JPG
Another project I intend to do is making some tail lights, maybe with turn signals, for my 1915 runabout with 6 volt LED bulbs that won't tax my little battery and mag charger.

Re: Headlight bulb non-starter

Posted: Thu Oct 17, 2019 7:50 am
by john in kzoo
Thanks to all. Anyone have some old bulbs for sale as Steve suggests?

Re: Headlight bulb non-starter

Posted: Thu Oct 17, 2019 5:44 pm
by George Mills
There is a reason that Ford had to abandon the whole magneto light at variable voltage. A- it doesn’t really do a lot and barely glows at idle, B- you get up to about 20 MPH and it gets (almost) bright enough to ‘see’ 3 ft in front of the radiator, and C- You get to 30MPH and the illumination turns into a search-lite and the filament explodes like an old Kodak camera flash. Everything in between becomes a crap-shoot.

The above experiences are NOT the result of old lamps, or tarnished bases, or tarnished reflectors, or squirrely grounds…this is the way they worked right off the lot!

In order to work at ‘rating’ (which my own research says was 18 cp originally) the maximum speed of the car with a well spaced mag would have to be 18 MPH in high, 7 MPH in low. That’s right, not a typo!

At 25 MPH the voltage to each lamp is on the order of 13v to each lamp which has a very nice benefit. The illumination goes to a whopping 4000 cp (that’s right too…), but the lamp life then comes down to the order of a second or two.

Changing voltage doesn’t help much. (there may be a 12V single filament, double pin based lamp, others would have to chime in as I’ve never found one) Let’s just ‘say’ you could find a lamp, ‘say’ rated at 12 volts AND 32 cp….

At idle of 400 RPM with the same mag clearance value it would push out maybe 1.5 cp and the lamp will last into the next century if that’s all it ever sees…
At 15 MPH that same lamp would be pushing out maybe 3.5 cp and last maybe some 1000 hours …
At 25 MPH woo hoo…you get all 32 cp and rated 200 hr lamp life too!

Unfortunately, the only GOOD solution is the one Ford itself took in 1917...go to single filament double pin 6V lamps and bury a Ford built choke in the circuit to shed voltage above 12V out of the mag. Full rated cp then at about 13 MPH and above, good average lamp life.

Playing with alternate lamp voltages is like playing with Facebook … it's complicated :)

Re: Headlight bulb non-starter

Posted: Thu Oct 17, 2019 11:43 pm
by Steve Jelf
With mag lights I'm afraid to go fast enough to burn out the bulbs. At that speed I would outrun the lights and end up in the ditch. :D

Re: Headlight bulb non-starter

Posted: Fri Oct 18, 2019 8:17 am
by john in kzoo
Found some 6 - 8 volt on ebay....Should be here next week.
It will be fun to see if/how they work

Re: Headlight bulb non-starter

Posted: Fri Oct 18, 2019 5:51 pm
by YellowTRacer
I ran a #1009 bulb for the magneto lights in my 1920 ice cream truck I don't remember what kind of bulbs that I first installed in 1965 but they didn't last long and neither did subsequent replacements. Then in around 1972 I put in these 1009 bulbs (I don't know any other description, volts, watts, amps, other than the number on the base) they lasted 40 years and are still in the truck although it never goes out at night any more. They were plenty bright at speed and adequate at 25 MPH. The truck has ribbed lenses so the bulb was not easily visible which was good because it's not a big great early looking bulb. It's a small bulb, looks like it belongs in an electric cowl or tail light, that size. But they worked great and I used to drive it at night at speed across the San Francisco/Oakland Bay Bridge.

Ed aka #4