Coil will Fire on Bat but not Mag?

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Model T Ford Forum: Forum 2016: Coil will Fire on Bat but not Mag?
Top of pagePrevious messageNext messageBottom of page Link to this message  By Philip Berg on Sunday, October 23, 2016 - 06:26 pm:

Weird issue, new points and capacitor. Car will start easily on bat all four coils fire, switch to mag one coil goes dead. Verified by shorting at plug.

Any thoughts?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Gregush Portland Oregon on Sunday, October 23, 2016 - 06:40 pm:

Did you switch the coils around to see if it follows the one coil?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Philip Berg on Sunday, October 23, 2016 - 06:47 pm:

Yes, I replaced the coil with a backup and it fires on mag no issue.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Gregush Portland Oregon on Sunday, October 23, 2016 - 06:53 pm:

It may have an open wire in the windings. Maybe there is enough amps/volts to jump the gap on DC battery but not on AC magneto.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Sunday, October 23, 2016 - 07:22 pm:

Get someone to test the out of adjustment coil on a hand cranked coil tester or a Strobe O Spark so that you can see what is wrong with it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Young in Mays Landing, NJ on Sunday, October 23, 2016 - 08:16 pm:

I'm having the same issue with two of my coils that were rebuilt maybe 3 years ago and had new points installed this past June. The whole set was sent out to Ohio, repointed, and adjusted on his HCCT. The first one died on the Finger Lakes Tour and the second went out a month later.


Top of pagePrevious messageNext messageBottom of page Link to this message  By James A. Golden on Sunday, October 23, 2016 - 08:40 pm:

If the coil was a recent repro, it may have been one that was built to only run on 6 or 12 volts DC.

I bought 4 like that and they would short out on the higher Mag voltage and not work well at all.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Eviston on Monday, October 24, 2016 - 01:56 am:

Ditto to James. The ones like that have a rough, light color wood case. KW stamped on some of them.Lighter in weight than T coil. J. C. whitney sold these in the 60's and 70's. They don't run well on Mag. There was an article, IIRC in Vintage Ford or T Times about these coils.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Monday, October 24, 2016 - 07:34 am:

Good comment, I forget this because I learned long ago to only use Ford coils as cores, so it doesn't happen to me again.

Those KW branded coils were sold by Sears, JC Whitney, and other retailers up through the 1980's. The windings are not as good as Ford windings, so even when you have a good working one they are somewhat inferior. There have been a couple different brands of aftermarket coils recently, not sure how they rate, but if you stick to original Ford coils then you won't have a problem.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Philip Berg on Monday, October 24, 2016 - 12:10 pm:

The coils that came with my 11 are K&W with a date of 1953 stamped in them.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Larry Smith, Lomita, California on Monday, October 24, 2016 - 12:19 pm:

Perhaps you magneto is weak.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis-SE Georgia on Monday, October 24, 2016 - 12:57 pm:

The OP didn't say whether the coils had been set up on a tester or just the parts changed out. If the points were changed and the coil was not set up on a HHCT ,et al, then that is likely the problem.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Monday, October 24, 2016 - 01:34 pm:

They can work OK if they are adjusted properly but they will never have the output of a Ford coil.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jim Eviston on Monday, October 24, 2016 - 01:42 pm:

Philip, those are the newer coils to which we refer.
When I got one or more of those, I would get a hold of one of my gas engine collector friends and trade them for real T coils of other things I could use. I think those coils may actually work better on a gas engine than a T because they will work when adjusted to draw only about half an amp.


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