Magneto output

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Oldav8tor
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Magneto output

Post by Oldav8tor » Wed May 04, 2022 9:36 pm

I bought a cheapie analog voltmeter to check my Magneto output. With the engine running and the throttle advanced 5 notches it reads 15 VAC. At about half-throttle it reads 28 VAC. If I rev it a bit the needle jumps over 30 VAC. Does this sound normal to you?

The engine was rebuilt in 2018 and a new coil ring and recharged magnets installed. I've put 5000 miles on it since then. It starts and runs very well on magneto.
1917 Touring
1946 Aeronca Champ
1952 Willys M38a1 Jeep (sold 2023)
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Steve Jelf
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Re: Magneto output

Post by Steve Jelf » Wed May 04, 2022 9:55 pm

The Electrical System book says 9.8 V @ 7.9 amps @ 400 RPM (10 mph), 18.8 V
@8.8 amps @ 800 RPM (20 mph), and 26.2V @ 9 amps @ 1200 RPM (30 mph).
The inevitable often happens.
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AndreFordT
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Re: Magneto output

Post by AndreFordT » Thu May 05, 2022 6:03 am

Tim,
an easy way to test your magneto:
You need to charge your magneto output by a 12V 21W light bulb between the magneto post and the frame. Than connect you Ac Volt meter between the post and the frame and run the engine the same way you did. You should fined the same test results. At the end, at high running speed, the ligh should blown out. Than you should see 30AcV+. Your magneto is working right.

I tought I had photos about it but it is a little film and I don't know how to post it on the forum.

Good luck.
Andre
Belgium
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Bill Robinson
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Re: Magneto output

Post by Bill Robinson » Thu May 05, 2022 8:26 am

The easiest test there is!
https://youtu.be/QnMUPNFbVWQ
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Quickm007
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Re: Magneto output

Post by Quickm007 » Thu May 05, 2022 10:15 am

Personnaly, I used the software Magneto Test Capability from Mike Kossor. Work really well and gave the right accurency. Bulb method work fine either but I'm scientific person who like to measure everything with fact. Both method will work but one gave you the exact output. It may not necessary https://modeltitimer.com/
Super Mario Bross ;)

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TWrenn
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Re: Magneto output

Post by TWrenn » Fri May 06, 2022 9:56 am

Or, just for the fun or heck of it, put one of these little accessories on ur car.

https://www.modeltford.com/item/A-MAGM.aspx
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Les Schubert
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Re: Magneto output

Post by Les Schubert » Fri May 06, 2022 10:42 am

Your magneto output sounds GREAT to me. Exactly what I would hope for.
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Oldav8tor
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Re: Magneto output

Post by Oldav8tor » Fri May 06, 2022 9:41 pm

Our club has a Fun Projects replica of a St. Louis Magneto tester. It is designed to show if a mag is producing a proper output and works at any RPM above idle. When I tested mine, it indicated output correct for a 1914, even though I have a 1917. Not a big deal as I'm not trying to run headlights, just the ignition coils.
IMG_2874.jpg
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1952 Willys M38a1 Jeep (sold 2023)
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Steve Jelf
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Re: Magneto output

Post by Steve Jelf » Fri May 06, 2022 11:57 pm

When I tested mine, it indicated output correct for a 1914...

That should be enough to start on MAG.
The inevitable often happens.
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Topic author
Oldav8tor
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Re: Magneto output

Post by Oldav8tor » Sat May 07, 2022 9:18 pm

My car starts very well on mag. I really can't complain.
1917 Touring
1946 Aeronca Champ
1952 Willys M38a1 Jeep (sold 2023)
1953 Ford Jubilee Tractor
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