Coil box function

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Model T Ford Forum: Forum 2015: Coil box function
Top of pagePrevious messageNext messageBottom of page Link to this message  By henry h on Monday, February 02, 2015 - 04:02 pm:

In trying to get wiring up to speed on a starter /generator T, I find there is continuity between the timer terminals on the coil box (1 to 2, 1 to 3, etc). This occurs with the wires from the timer unhooked. After looking at the diagrams on this site, i put together a sketch of the circuit to try to understand. If i have the diagram right, then when the coil box contacts are in their normally closed position, there is continuity between each timer terminal on the coil box and the brass strip that connects each of the coil boxes through the contact on the bottom of each coil box. But if that is right, then how does each plug fire by itself? What am i missing?


Top of pagePrevious messageNext messageBottom of page Link to this message  By JohnH on Monday, February 02, 2015 - 05:37 pm:

The diagram is correct. There is a circuit between all three terminals of the coil. So, when 6V is applied to the + terminal, 6V will be present at the other two terminals, until the timer contact is grounded.
The coil won't produce high voltage until the timer contact is grounded because until then, there is no current flow in the primary. Sufficient current flow must occur in the primary coil to attract the lower point and thus repeatedly interrupt the current. Then the transformer effect can occur and provide a stepped up voltage from the secondary.


Top of pagePrevious messageNext messageBottom of page Link to this message  By George_Cherry Hill NJ on Monday, February 02, 2015 - 06:18 pm:

Think of it this way...

The hot side is always hot, even on all 4....

The comm wires are actually 4 individual ground wires that are isolated from ground at the timer.

As the timer roller/brush makes contact with each of the 4 individual contact lugs of the timer cover while it rotates inside the timer, the ground is created...4 times per cam revolution...


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Monday, February 02, 2015 - 06:27 pm:

Henry
When trouble shooting any of the timer wiring you must remove all four coils from the coilbox.
Here is a correct wiring diagram you might find helpful.
1
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Monday, February 02, 2015 - 06:57 pm:

Ron is right. If everything is correct on the coil box a good set of coils will make a spark at the spark plugs. The coils should be tested and adjusted separately from the coil box, with a coil tester. If they test good, and the coil box wired correctly, they should work.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tony Bowker on Monday, February 02, 2015 - 06:58 pm:

The item missing on your schematic is the inductive coupling between the primary and secondary. When the contact closes, current flows in the primary. When the contact opens, the interruption of current induces a very high voltage in the secondary, causing the spark...


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Monday, February 02, 2015 - 10:01 pm:

Here's Ron's diagram without the paper.


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