Engine dies when lights turned on

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john in kzoo
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Engine dies when lights turned on

Post by john in kzoo » Mon Oct 12, 2020 8:03 am

Guys,

I think I know the answer to my question; I re-wired my lights to run in parallel from the original series. Runs fine on battery (12v) with lights on, switch to mag, engine sputters and dies. I assume the mag isn't able to generate enough electricity to power everything.
15' touring, (2) 6-8 Volt tung sol vintage bulbs


Mark Osterman
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Re: Engine dies when lights turned on

Post by Mark Osterman » Mon Oct 12, 2020 8:08 am

When was the magneto last rebuilt?

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john in kzoo
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Re: Engine dies when lights turned on

Post by john in kzoo » Mon Oct 12, 2020 8:39 am

1915 :lol:

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Oldav8tor
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Re: Engine dies when lights turned on

Post by Oldav8tor » Mon Oct 12, 2020 10:40 am

I'm wondering how you wired the lights so as to run off either battery or magneto? I added a 12 volt battery to my car and run the lights off it only. I also converted to LED's but that is another story.. I wonder if you are somehow grounding out the magneto?
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Re: Engine dies when lights turned on

Post by Norman Kling » Mon Oct 12, 2020 10:52 am

The magneto lights were intended to be wired in series. If you put them in parallel, you draw more from the magneto than it can deliver to both lights and ignition. You either need to wire the lights and use the bulbs as originally wired, or run the lights only from the battery. Depending on how much night driving you do, you will need to charge the battery between uses. If you do much night driving, you will need a generator or go back to the original wiring.
Norm

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john in kzoo
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Re: Engine dies when lights turned on

Post by john in kzoo » Mon Oct 12, 2020 10:59 am

Here is how I have it wired.
Red and blue on top of the switch are hot to the lights, each light is grounded on their respective radiator mounting bolts.
Blue (under the spark plug wire is hot from battery

Thanks in advance

John
Attachments
light.jpg

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Re: Engine dies when lights turned on

Post by Oldav8tor » Mon Oct 12, 2020 11:20 am

So....your lights only run off the magneto if I'm seeing the wiring correctly. I assume the battery post is only connected to the 12 volt battery. Norman may have it correct although I would think there would be enough juice at high rpm to keep the engine running albeit perhaps poorly. I think if you choose to run the lights off battery and install the appropriate bulbs you will have more reliable lights than the magneto bulbs. I went to LED'S which draw a lot less juice and are brighter than the available incandescent bulbs. I don't have a generator and use a battery minder to keep the battery up. My battery is a small AGM unit so if you have a conventional car battery installed you'll have a lot more reserve than I have so running lights shouldn't be a problem. I use my battery for starting and then run on mag.
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Re: Engine dies when lights turned on

Post by john in kzoo » Mon Oct 12, 2020 11:34 am

I wonder if I could relocate the far right connection from the mag terminal to the terminal with the blue connector (under the plug wire). The result should be that the car will run on mag and the headlights will run off the battery........Correct?


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Re: Engine dies when lights turned on

Post by Been Here Before » Mon Oct 12, 2020 11:38 am

Posting for no reason - wiring for 1915.
89148wiring1915.jpg
89148wiring1915.jpg (19.81 KiB) Viewed 338 times

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Re: Engine dies when lights turned on

Post by TonyB » Mon Oct 12, 2020 11:52 am

I think your diagnosis is correct.
The magneto might be a little weak but I doubt even a rebuilt one could supply two six volt bulbs in parallel. A simple solution requiring no rewiring would be to switch to twelve volt bulbs. 😊😊
Tony Bowker
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1914 Touring, 1915 Speedster, 1924 Coupe.

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john in kzoo
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Re: Engine dies when lights turned on

Post by john in kzoo » Mon Oct 12, 2020 11:59 am

Thank guys. I don't do much driving at night (the occasional gas light parade) so, if I relocate the far right connection from the mag terminal to the terminal with the blue connector (under the plug wire). The result should be that the car will run on mag and the headlights will run off the battery........Correct

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Re: Engine dies when lights turned on

Post by Mark Gregush » Mon Oct 12, 2020 12:00 pm

john in kzoo wrote:
Mon Oct 12, 2020 11:34 am
I wonder if I could relocate the far right connection from the mag terminal to the terminal with the blue connector (under the plug wire). The result should be that the car will run on mag and the headlights will run off the battery........Correct?
Yes, that should work.
I know the voices aren't real but damn they have some good ideas! :shock:

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Re: Engine dies when lights turned on

Post by Been Here Before » Mon Oct 12, 2020 12:02 pm


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john in kzoo
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Re: Engine dies when lights turned on

Post by john in kzoo » Mon Oct 12, 2020 12:07 pm

No, the mag was not tested.

I'll move the connections tonight and run the car on mag while having the lights on battery

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Re: Engine dies when lights turned on

Post by George Mills » Mon Oct 12, 2020 1:12 pm

I see your wiring totally different.

If your inside switch is wired correctly...

It looks to me like the lower right RED crimp ferrule connection is on MAG post of the coil box??....the lower left BLUE crimp ferrule is on BATT post ??

Thus you still have MAG voltage going to the light switch, and then two parallel 6-8V lines coming out the top of the dash light switch? Then, where on earth does the BLUE ferrule crimp on the lower left go to? (I hope it is to wherever you have your battery located) Wired this way, your lights just might illuminate at idle, but you give it some RPM and they go poof.

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Re: Engine dies when lights turned on

Post by Mark Gregush » Mon Oct 12, 2020 1:23 pm

He explained where the wires go in his post(s). Lets not over complicate a simple thing like changing a wire for the power source. Other then the extra wire for the head light, it is wire now as it would have been with a battery added.
I know the voices aren't real but damn they have some good ideas! :shock:

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john in kzoo
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Re: Engine dies when lights turned on

Post by john in kzoo » Mon Oct 12, 2020 1:40 pm

George,

Blue crimp connector goes to my battery under the backseat.

Guys,

Another stupid question, I have both a 6 volt battery (currently not using), and a 12 volt battery to start and then switch to mag. I should run my lights on the 6volt as again they are old tung sol 6-8 volt incandecent bulbs

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