Hi all
My girlfriend's dad has a 1937 Chrysler/ Plymouth six cylinder positve earth. This week the wire from the coil to the ignition switch burnt out. Two Q's really
1 He wants to test the coil before ordering a new one. It doesn't smell cooked up. Can anyone point me towards how to do this please? He does have an old krypto tuning station (massive thing) & there is a massive manual with it. I was hoping not involve it as the manual alone looks like a week's worth of reading.
2 The initial fault. Any ideas, or could it have simply have been a component failure or chaffed wire to earth? Obvioulsy had a huge amount of current flowing through it.
The car was out on a run when this happened. I don't know wether it occurred during the run, or on start up.
Damn odd points in it. Single sided with the other contact attached to the base plate itself with like a crude vernier adjust.
That reminds me-emailing USA specialists isn't forthcoming on finding an electronic ignition replacement. Can it be THAT hard? I can use a soldering iron & did have some basic electronic training years ago, so I'm not frightened to have a go! Thoughts?!
Thanks all. Makes for a departure from my diesel & dog ones!
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-emailing USA specialists isn't forthcoming on finding an electronic ignition replacement. Can it be THAT hard?
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Just a suggestion. Would it not be better to search out an owners club or more. They would probably be a better source of information on all aspects.
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To test the coil, first, disconnect all the wires that go to it.
Make up a test lamp out of an old sidelight bulb and holder.
Attach one lead of your test lamp to the live terminal of the battery (negative in your case) and touch the other lead onto the live terminal of the coil (possibly marked up as SW). The bulb should not light. If the bulb lights, the coil primary winding has shorted to earth, and is therefore unservicable, and a possible cause for your burnt out wire.
Connect the vehicle's live ignition feed wire to the coil, and turn on the ignition. With the test lamp, make sure this terminal is live.
Then make sure that the other low tension terminal (possibly marked CB) is live. This checks the continuity of the primary winding.
Now, reconnect the vehicle's low tension wire between the coil and the distributor, leaving the test lamp on the CB terminal. With the HT output of the coil connected to earth, turn the engine over. As the points open, the test lamp should light, as the points close, the test lamp should go out. i.e., you should see the lamp flash rapidly as the engine turns.
All that checks the low tension side of the coil assuming all is well here, now consider the HT side.
To check out the HT, rig up a spare spark plug (with a nice wide gap - 50 thou or so) and lead so that the metal body of the plug is earthed, and the HT lead is connected to the coil. Switch on the ignition, and turn the engine over - you should see a stream of fat blue sparks.
Also, you can check out the coil with a resistance meter.
The primary winding should be a few Ohms. There should not be continuity to the case of the coil.
The secondary winding can be checked by an Ohmeter between one primary terminal and the large HT terminal. You should read a few KOhms, again with no continuiy to the case.
I hope that helps,
Number_Cruncher
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Either mounted outside the distrubutor or inside is a capacitor in a metal can ( Condenser ) old speak. These can fail short cct so Number-Cruchers test is valid but if you connect the distrubutor and the lamp still lights when the points are open then disconnect the capacitor if the light goes out then there is the fault. This shorted capacitor will have stopped the car and if the ignition was left on for any amount of time it would have heated up the coil but it should not of melted the wire so a short circuit coil or the RF intererence capacitor that may be fitted next to the coil may be your problem. As frar as electronic ignition goes 'Lumignition' used to make a straight contact set replacement unit and a rotar ( IR Optical )unit but whether it goes back to 1937 I do not know. Regards Peter
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Yes, Peter is right to include a test of the capacitor.
If I understand Peter's test correctly, it is done with one lead of the test lamp connected to live, and the other end connected to the terminal on the disributor. So, when the points are closed, the cicuit is complete and the lamp lights, and when the points are open, the lamp should go out - if not, short circuit in the capacitor, or possibly in the wiring to the points.
The test as I described was with the low tension circuit connected as per normal operation. With one lead of the test lamp connected to earth, and the other test lamp lead also connected to the CB terminal of the coil. In this configuration, the test lamp lights up with open points, and goes out with closed points. A short in the capacitor would mean the test lamp would not light when the points are open.
Both test methods work - it is just that the logic between points being open and light being on or off is inverted.
If it does turn out to be the capacitor, you might struggle getting an exact replacement. Some types of distributor of that sort of age used capacitors where the can was soldered in place into the distributor baseplate rather than simply being screwed down!
Number_Cruncher
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An old coil may still work but be well down on output voltage.A new coil is not that expensive anyway.I've used Lumenition in the past and they are the best electronic ignition conversion there is but not cheap,incidentally you would still use the standard coil.
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Using a spare coil::::
Those coils in Alluminium cans with the black plastic top(Lucas/AC Delco etc. IIRC) that have two tags to push the wires onto are oil filled for internal high voltage insulation and the storage life is usually very good -- it was the very early non-oil ones that were usually painted that were unreliable.
If you take a wire from the coil spark connection and offer it close to the car metalwork the spark will usually jump about 3/8ths of an inch and show it has plenty of umph -- about 19Kvolts actually. Watch your fingers. Use a plug wire type or wrap the wire end round a plastic stick/tube and hold the tube, as a spark through your fingers is not very pleasant.
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Many Thanks all
Now I have a agenda for my Sunday!
FYI the coil is also a slightly odd config-usual HT output but only one contact engine side, the other on the back of the coil in the bulkhead. No idea if it was oil filled. Would very much like to retain this particular coil to maintain original condition, well not the non-working condition-you know what I'm attempting to say!
Virtual drinks at the bar for all. Chin, chin.
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Ah, that will change how to check the secondary resistance. I gave the checking procedure for a more modern coil where one end of the HT is connected to the LT circuit within the coil.
Vehicles with an insulated return electrical system also have coils with four terminals rather than three.
In more modern vehicles, prior to the introduction of coil packs and individual coils, coils were very reliable - I've only ever replaced a handful of them. However, I can imagine a near 70 year old coil might not be as well insulated as it was when it was new. Having said all that, the checking methods given above should enable you to determine where the fault really lies.
Number_Cruncher
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Is 1937 the date of manufacture or a style of car? If the former, it could have had a 6 volt battery and needed a 6 volt coil. 1937 was also about the time many cars were using magnetos.
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Obviously 1937 manufacture from what you posted while I was typing.
I doubt very much that your coil is oil filled.
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