coil rebuild.

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Model T Ford Forum: Forum 2018: coil rebuild.
Top of pagePrevious messageNext messageBottom of page Link to this message  By Allan Bennett - Australia on Saturday, April 14, 2018 - 08:15 am:

I have been working on a set of coils for Henrietta and have 6 ready to repot. These are giving me grief.



The two on the left have me flummoxed. The one with the new capacitor fitted passes all the usual tests, but will not show a spark on my Fun Projects strobe tester. I removed the points and condenser from the other one because it was doing exactly the same thing! It did fire up initially for just a couple of seconds, long enough for me to see it needed no further adjustment. Then nothing.

The third coil is wired differently from all the others and I am not sure how to make the connections. If it is like the others, the long wire from the bottom, the multi strand wire from the coil point lug and one end of the condenser should be cońnected. The other condenser wire goes to the outer stud, but there is no other wire from the top end of the coils. What am I missing?
,
Allan from down under.


Top of pagePrevious messageNext messageBottom of page Link to this message  By BRENT MIZE on Sunday, April 15, 2018 - 08:54 am:

Hi Allan,
The two coils that fired initially are most likely firing internally. If that’s the case, they are not rebuildable.
The KW stamped box is wired differently with the terminals reversed.
The wire leading up from the primary is soldered to the tab in the upper left hand corner along with one lead of the cap. The lead extending from the upper right hand terminal goes to the other lead of the cap.
I hope this helps.
Brent
The Coil Doctor


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mike Kossor - Kenilworth, NJ on Sunday, April 15, 2018 - 01:08 pm:

Allen, was the new capacitor of the correct type and dv/dt rating? The wrong type of capacitor can fail as you described.


Top of pagePrevious messageNext messageBottom of page Link to this message  By kep on Sunday, April 15, 2018 - 05:40 pm:

I have done 12 of these in the last month. Sometimes... when it's a puzzle. You have to take the whole coil box apart and examine everything in detail.
The 2 that won't spark, you may, if you can freeze and break off the tar, find that the paper insulation is decayed and burnt. Where it burns through you might find an internal short, in which case you can probably repair that winding and wrap fresh paper on (nail polish as an insulation maybe? I'm rough though.)

As for the other one... all I know... is that sometimes you have to pull it completely apart to find the missing wires.


Top of pagePrevious messageNext messageBottom of page Link to this message  By George Andreasen on Sunday, April 15, 2018 - 05:53 pm:

I just tried to re-cap one of my coils and despite being careful, I managed to break that hair fine wire UNDER the tar. I may try to salvage it by further "excavation" but it's pretty easy to do without noticing!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Allan Bennett - Australia on Sunday, April 15, 2018 - 08:13 pm:

Thanks fellows. Mike, the capacitor is the orange one the vendors sell for the purpose. The other six work well and this one tests OK.

Brent, your help is appreciated. The coil with the capacitor fitted did not fire at all. The one from which it was transferred fired well for a few seconds before dying. The KW wiring makes sense now. I will connect it up and see what comes of it.

Kep, I have enough coils to be able to give these faulty ones a miss. I am quite adept at letting the smoke out of electrical components, and will pass on your suggestion. You can have them both for the price of the postage if you want to give them a reprieve. The boxes are nice!

Allan from down under.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Allan Bennett - Australia on Sunday, April 15, 2018 - 10:22 pm:

Update. Brent, I have soldered the connections on the KW coil and it works nicely! Thanks. Now I have to scrounge up enough tar to pot them. Your roofing tar is not used in Australia so I may have to melt some out of dead coils. I usually hold the condenser in place with a large gob or two of silicone, but a couple of these coils are threatening to come loose in the case, so I need to do the job properly on these.

Thanks again, Allan from down under.


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