I wired up the mag lights on my 1915 touring and when I turned the light switch on, the car shut off. It must be grounding the mag out and shutting the car off. I wired the lights according to the wiring diagram I have, any thoughts on this one? There is a ground wire going to the frame (which originally was grounded the radiator mounting bolt). Can someone tell me what happened here?
I can't imagine that those two little bulbs would suck up all the juice. Sounds like there's a hidden ground somewhere between the MAG terminal on the coil box and the first bulb. Maybe in the socket?
One of two things is happening.
One: The extra load on the magneto provided by the lights is too much for the mag, and it can't put out enough juice to run both at once.
Two: There is a short to ground somewhere in the lighting circuit. It could be in the switch, the wiring, one of the bulb sockets, or a bulb.
Here's my suggestion for a trace: First, remove the wire going to the lights from the switch. This is most important, because it eliminates the possibility of back-feeding the mag, and discharging the magnets. Then, make yourself a "tester" consisting of a bulb and a battery. It can be any size bulb and battery that work together. Hook it up so that it goes from the lights wire - to the bulb - to the battery - to ground. If it lights the bulb, you have a short to ground in your lighting circuit. If it lights dimly, you have no short to ground, and the current is flowing through the two bulbs, adding extra resistance. To make sure, remove the two bulbs, and you should get no light from the tester.
If you have no short, you have a weak magneto that can't handle the load. You ARE using magneto bulbs, aren't you?
One other possibility is a short to ground inside the switch itself. Easy to check out - start the car with the wire to the lights still disconnected from the switch. Turn on the light switch. If the car keeps running, the short isn't in the switch itself.
If you have a short, start tracing! Your objective is to make the test light go out. First, try shaking wires all along their path, and see if the test light flickers. Then, remove the bulbs. Then remove the wires from the sockets, starting with the one farthest from the source. Somewhere along the line, you'll find the short. Fix it, and you'll be good to go!
The thought of a ground in the switch occurred to me, but in a 1915 the switch is mounted in a wood firewall.
Pete has some very good suggestions. I'm with him on a number of points. Wrong bulbs, possible short and a weak mag. I'd leave the switch for last but it's definitely in the mix. You can, if you have an ohm meter, disconnect the feed wire to the bulbs and hook the meter to the wire going back to the switch (mag. wire disconnected). Turn the light switch on. If the meter reads ground you have a bad switch but the easier stuff comes first. You can run the engine at a higher speed and turn the lights on too. If the mag puts out more at a higher speed and they stay on and the eng keeps running you'd have a weak mag.
I don't understand how a switch mounted on a wood firewall could be the problem. If the switch is open, the current stops there. If the switch is closed, the current runs on down the wire to wherever it's going. If the switch is defective and the current is reaching the body of the switch, so what? It's mounted on WOOD, an insulator, so the current is NOT going to ground at the switch. If I'm wrong on this, maybe somebody can explain it to me.
Is this how you wired your lights?
Steve is right, unless of course there is a path to ground somewhere. I am not familiar with wood-dash cars, so I can't even imagine any such path --- EXCEPT if the wood is wet, or painted with a conductive paint of some kind. It does seem hardly likely, though.
It sure looks like the picture above is a metal firewall (by the way, I meant "firewall" in my post above, not "dash").
Are you sure your car is a 1915 Model T? My 1916 still has a wood firewall.
It's not a metal fire wall. It's the wood firewall on my dad's '17.
Look again, guys. The firewall in Erik's picture is wood. When you look in the holes for the coil box terminals you can see how thick it is. But we haven't seen Alex's firewall. There's no picture of it so far.
The bulbs you are using must have 2 contacts at their bases. They must have a single filament whose ends connect to the 2 contacts. No part of the filament is connected to the socket side portion (brass housing) of the bulb. These type of bulbs are not commonly bought at NAPA or any other regular modern parts dealers. Original Mag bulbs were rated at 9V each for a total of 18 volts when placed in series. They don't last very long and if you rev up the motor they last even shorter time. I just wondered if you perhaps trying to use a modern bulb of some sort that had a single contact at its base connecting one end of the filament and the other end of the filament grounded to the bulb side in the usual manner. That type of bulb is not going to work in a '15/'16 series string arrangement.
Can we say "over restored?"
Heh Heh Heh! not a visible wood grain anywheres!
Looks like the car in Erik's pictures has one 1917 headlamp and one later. Look at the position of the focus adjuster screw.
You are correct, Mr. Peterson - the driver's side lamp is the original and correct E&J and the passenger side is a later replacement.
About 60 years ago when my dad was driving the touring the passenger side headlamp yoke broke where it meets the bracket and the headlight bucket was dangling by the wires. This is not a common Model T Ford problem but it has been known to happen. Don't know if it due to a stress fracture caused by years of vibration or just a bad casting/forging from new.
My dad replaced it with a later lamp.
The original broken headlight is sitting on the shelf. My dad has a correct replacement E&J but has not gotten around to restoring it and installing it on the car.
Right at this time there was a lot of transitional changes 9/16, 5/8 and 3/4" magnets were around, small round single and double stack mag coils were available, as were single and double stack larger oval mag coils. Early mags only put out 12 - 16 volts and later ones put out 18 volts with the bigger coils. You have to be assured that you have double contact single filament bulbs. 6 volts will work ok, 12 volts may be too much, 9 volts is best, however 9 volt lamps don't exist any more. There is an option that you can do with the 18 volt output from your mag you can wire a third 6 volt lamp in series and hide it under the car or put three lights out front all 6 volts in series If one goes out they all go out like the old christmas tree lights. This was the technology of the day as in 1915 was the lead year for electric lights. I don't think Mr Ford had much moxy on this new type of wiring so I think his friend Edison offered the wiring program. The wiring method was very soon modified by after market people to a parallel system some using external batteries that had to be charged from an external source. Ford very soon followed up with parallel wireing that prevented the blackouts. I don't believe the switch is the problem it is most likely at the socket assembly.
Thanks everyone for the great responses. My car has a newly rebuilt engine, mag and transmission, so a weak mag is out. It has original mag bulbs and its a 1915 so it has a wood firewall. It is wired correctly. I have to be missing something. I am going to take a look at the wiring again. But again, the second the switch is pulled the car shuts off immediately, So when the switch is pulled it grounds the mag out which shuts the car off. I just dont get how its grounding out the mag. I am going to work on the car tomorrow (saturday) so I will take a look.
Strategically disconnect wires in the system and see when the problem goes away. For instance, disconnect wire at right headlight. Does it still go dead when you turn on the switch? If so, the problem is in the wire to the light (or switch, but that's not likely).
Thanks to Buzz Pound here are some details about the evolution of the Model T magneto physical design.
Ron the Coilman
It's off topic, but does anyone else notice the optical illusion that the chart stimulates? I see small white dots everywhere a black line intersects a pink line.
There were a number of harnesses built a few years ago that would succumb to short circuits in the area where the wires are loomed together. My recollection is that the problems usually resulted in crossfire between timer wires but it could probably result in a headlight short too. The harnesses I'm thinking of had the metal reproduction Ford tag in the loom. Theory was that the tag prongs managed to work through the insulation on the wires.
Just one of the possibilities.
Erik, same thing happened to our '17 while on the Centennial Tour in Richmond. One of these days I'm going to try to have the stem welded back onto the yoke by removing the bucket and getting it welded from the inside as well as on the outside.
According to Ford, the change from the 1/4" wide magneto copper to the 3/16" occurred in the spring of 1921. Just sayin'.
I figured out the problem. The bulbs were not the correct bulbs. I installed original blown glass mag bulbs in my lights and they worked! So thanks for the help.
So then do I win a prize or something
Yes John you get the boobie prize. Thanks!
We'll even give you a choice of a red footed or blue footed booby!
Check the headlight plug, you have the later which the pin are horizontal the headlight should have vertical pins to match the correct 90 degree headlight plug. Ed Henline