Magneto question

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Model T Ford Forum: Forum 2018: Magneto question
Top of pagePrevious messageNext messageBottom of page Link to this message  By William Hoffer on Tuesday, February 06, 2018 - 11:59 am:

Should every coil be connected with a bridge to its neighbors, or is there supposed to be a break at some point? How do you test for continuity on the coil assembly? Thanks!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis-SE Georgia on Tuesday, February 06, 2018 - 12:37 pm:

Not sure exactly what you are asking. Physically, the coils are not attached to each other at all. They just sit down inside the coil box. Electrically, the bottom terminals are all connected to one another. This where it gets its power from either the battery or magneto, depending on ignition switch position. The upper side terminal gets grounded by the timer and completes the primary circuit, allowing the electricity coming in the bottom terminal to flow through the coil's primary winding and back to ground. The lower side terminal is the high voltage to the spark plug.


Top of pagePrevious messageNext messageBottom of page Link to this message  By William Hoffer on Tuesday, February 06, 2018 - 12:45 pm:

Sorry, I was not clear. I am asking about the magneto ring adjacent to the revolving flywheel magnets. The coils that generate the electricity that runs the car. It looks like there is a "bridge" or a connecting wire that goes from coil to coil all around the coil ring that is bolted to the back of the block. Is there supposed to be a break or gap in the ring? That is, are there 2 coils that are not connected together for some reason? And if all coils are supposed to be connected to each other, is there a way to check this with a multimeter? The engine is in the car.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tim Rogers - South of the Adirondacks NY on Tuesday, February 06, 2018 - 12:45 pm:

William, yes they are connected together.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Andre Valkenaers on Tuesday, February 06, 2018 - 12:52 pm:

William,

In the magneto each coil is connected to is neighbor. They are alternating in winding direction, a left hand coil is followed by a right hand coil. Together they make a loop of 16 coils. One end of the loop is connected to the cast iron core and the other end is connected to the post terminal.
You can make a test with a Ohm meter to find if the loop is open. A short loop is hard to find with it. The resistance of a good loop is very low 2 to 4 Ohm.

Hope this helps

Andre
Belgium



Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis-SE Georgia on Tuesday, February 06, 2018 - 12:55 pm:

William,

Sorry, I misunderstood. The 16 coils on the coil ring are all connected in series. One end is grounded to the metal ring and the other end is attached to the solder pile where the magneto post contacts it. If you were to take the ground end loose from the metal ring, you should get continuity from the solder pile to the end you just removed and no continuity from either rend to ground. However, I wouldn't want to take it loose. Also, the resistance is so low through there that I doubt a resistance measurement would tell you much. At least not with the elcheapo multimeters I have. What I consider to be a better method is attaching something like a D cell flashlight battery to the coil and take a hacksaw blade or similar and check each pole piece for magnetism. If there is a break or a short, the magnetism will quit beyond the coil that is grounded or opened. Work quickly, your wires from the D cell will get warm, as you are looking at almost a dead short.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis-SE Georgia on Tuesday, February 06, 2018 - 12:58 pm:

Actually, my test will only find a short. If it were open, none of them would show any magnetism, unless you had a open AND a short.:-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By William Hoffer on Tuesday, February 06, 2018 - 02:43 pm:

It sounds like I should get the engine running on battery and see if it will run when I switch over to mag. First start is about a week away unless things continue to pop up. Assuming it runs on mag, how do you test output? It either works or does not work?

Thanks for the replies and pix!


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Zibell, Huntsville, AL on Tuesday, February 06, 2018 - 04:51 pm:

William, This works. Place this phrase "test magneto mtfca.com" into a search engine. You will get good results.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Andre Valkenaers on Tuesday, February 06, 2018 - 05:05 pm:

William,
connect a 21W 12V lamp between the magneto post and the frame. Connect a Ac volt meter (need 40 Vac) over the lamp. Best use a needle volt meter
Run the engine on battery. Idle will light up the light and the volt meter will give 8 - 9 Vac. speeding up the engine, The light will get brighter and the voltage will go up, about 28 Vac is OK. Normally the lamp will blow out, this means you have a good working magneto.

Good luck
Andre
Andre


Top of pagePrevious messageNext messageBottom of page Link to this message  By James A. Golden on Tuesday, February 06, 2018 - 05:14 pm:

If you wish to invest about $100, you can buy one of these meters from the Spin Doctor to measure the magnetic strength of each coil's pole piece to ensure they are all functional.

Meter

Go to gravitastech.weebly.com for details.


Top of pagePrevious messageNext messageBottom of page Link to this message  By James A. Golden on Tuesday, February 06, 2018 - 05:17 pm:

You can apply as little as 6 volts to the coil ring to energize the coils for measurements.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Thomas Mullin on Wednesday, February 07, 2018 - 04:07 pm:

James, Can you test the magnets strength in car, or do they have to be individual? Oh, and what is the range of acceptable readings?


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