How are the mag headlights wired? I guess a wire would run from the mag post to the switch on the column, or from the mag post on the coil box to the switch then from there to the headlight on the driver? or passenger? side. Then from there to the other headlight. Since they are wired in series I suppose only the last one would be grounded. Can anybody explain how to route the wires? I've got a good mag and headlights so I might as well wire them up. Thanks.
I have my mag powered lights wired in this manner:
I hope that this helps. Bill
1915, 1916, 1917 and early 1918 shown here (switch on the firewall).
Originally, the ground wire on the left headlight was soldered to the radiator crossbar inside the engine compartment and not wrapped on the radiator stud.
If you have the combo horn button light switch, it has a dimming function which requires a coil.
An additional note, the 15 head lights were 9 volts in series and they offered the correct required resistance. If you are using 6 volt lamps they may be ok if you don't rev it too high. An alternate option is to wire a third 6 volt lamp in the same series circuit and either display the lamp or hide it under the car. With the third lamp you will be creating 18 volt load and that is what the mag is capable of.
I respectfully suggest that while I agree that the bulbs were both 9V bulbs and wired in series they could handle 18 volts OK, the magneto typically at high RPM puts out more like 28 Volts and thus the bulbs quickly burned out and Ford did not solve this problem during 15 and 16. Adding a third 6V bulb to bring the total bulbs to 18 doesn't solve the issue of 28 volts being applied to 18V bulb string. Better to put a dimmer coil in there and hide that since the dimmer coil had an AC resistance (called reactance) that increased with increasing RPM and thus allowed the bulbs to survive the increased RPM. Ford used the dimmer coil for a long time on the "cheap" car that had magneto headlights.
There have been a lot of questions about model T wiring and someone usually helps by posting the picture Bill provided. (thanks Bill)
It is very good except as I get older it is hard to follow where the wires go so I did a slight redraw showing how my 19 without a starter was wired.
I left off the plug wires to keep it simple.
If you use a battery for the coils when starting the battery is connected to the battery terminal and frame. (either polarity)
Then the switch on the coil box can select either the battery or mag for the coils. (usually the battery for starting and mag for running)
The horn and lights only run on the mag.
Thanks guys you showed me how to edit!
(Message edited by nhusa on November 02, 2015)
Is there a by-pass in that mag/head light circuit or when one bulb goes out do the both quit?
Both quit, just as on the old Christmas tree lights.
For those of you with 15-17 cars please note that the wiring for the horn was not the same as 1919 as correctly posted by Fred. In '15 and '16 the horn was wired from the magneto post on the coil box directly then to one connection on the mag horn. The other connection on the mag horn then ran up the steering column to a single button that grounded the horn to the steering column housing to complete the circuit and honk the horn. With the advent of the "combo" horn/light switch the wiring ran as show for the 19 above except the mag wire could also be connected to the dim and bright connections of the switch there so there were a few more wires in the tube running up the steering column. 15/16 had only one wire in that tube. Combo switch cars had a few more wires in there and hence the tube was bigger in diameter by a small amount.
Here's one more diagram of the pre-starter arrangement.
Rehash of the rehash….
Just look at my first post above and click on the second link. In that link, the combo horn switch T-8650 is shown in the Service bulletin diagram posted by Phil Mino.
You didn't bother to tell us the year of your car! Why not, it's kind of important. The Ford service book has that diagram for later cars.
He said that he had the switch on the column which I presume is the combo horn light switch.
Information for wiring either the dash switch or the column switch was provided early on in this thread.
Seems strange that it would be a series circuit since you'd lose both bulbs if one died. Any reason for that? Does it handle the vairying voltage better or was it just cheaper?
I have never tested a Ford magneto but in Dykes fifteenth edition it states (in the model "T" section) that "T" Fords were fitted with an 18 volt magneto and therefore to use 9 volt head lamps.
Also in the section of Mazda lamps it mentions that Ford magnetos were 18 - 24 volts and if 6-8 volt lamps were used then a reactance or dimmer coil (Ford part #8892 @50 cents) should be used. It also notes that better results were obtained by using two 9 volt lamps. It is understood that these early electric cars were produced with two 9 volt lamps in series and if you so chose to install 6-8 volt lamps then the reactance or dimmer coil was required. This is my limited understanding with what I have read, I have never tested a Ford magneto.