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Should I rewire hot to coil ?  Rate Topic 
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 Posted: 05-13-2018 10:12 pm
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browndog9
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I had a complete loss of power to plugs while traveling down the highway. I started tracing voltage and noticed that the wire supplying the coil was bare from the harness fork to the coil. This is a 75. Should I just rewrap the wire or replace with a new one. The car has a petronix and I could easily get a coil with an internal ballast.

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 Posted: 05-14-2018 06:49 am
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Esprit2
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Is the Pertronix the basic Ignitor, or the Ignitor II? The original Ignitor is current sensitive and can fry in short order if the ignition switch is left on for more than a few minutes without the engine running. If you plan to do any diagnostics, then get your ducks in a row, switch on, do what you must do, then switch off right away.

If enough current went through the coil wire to melt the insulation off, then it's very possible that a basic Ignitor is already fried due to the heat.

Is your JH a roadster or GT?

In the GT, the last bit of wire going to the coil is KW (pinK-White), and the insulation is a woven strand. That's a Ni-Chrome resistive wire, and the wire 'is' the ballast resistor. If that is what is present, then do not add a coil with an internal ballast resistor. That would be two resistors in series, and the coil wouldn't put out enough spark to be of any use.

The roadster has a White wire to a separate, discrete ballast resistor, then a WY (White-Yellow) wire from the resistor to the coil's (+) terminal. If you install a coil with an internal ballast resistor, then delete the discrete resistor... whichever kind it is. It would be easier so simply use a coil without an internal ballast resistor.

In either case, a second WY wire also goes to the (+) terminal. It comes from the starter solenoid, and is a direct feed that bypasses either stock ballast resistor, and delivers full system voltage to the coil for a hotter spark during starting.

With the ignition switch turned to the 'Run' position, is there (+) voltage in the naked wire? Switch off right after checking. There should be full system voltage before the ballast resistor, and around +8 volts at the coil (after the resistor). If there's no voltage, that's the circuit problem. Find out what is wrong and fix it.

If there is voltage at the coil's (+) terminal, then what is the voltage at the (-) terminal? If there's no voltage, then the coil is dead, replace it.

If there is voltage, it will be something less than at the (+) terminal due to resistance loss through the coil's primary windings. If there's voltage at the (-) terminal, and in the wire to the distributor, yet there's no spark, then the problem may be (most likely is) in the Pertronix's amplifier. Clean all Pertronix wiring connections, then check for security and continuity. If everything checks out, and there's still no spark, then it's a good bet the Ignitor's amp is fried. Replace it.

Regards,
Tim Engel

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 Posted: 05-14-2018 12:39 pm
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browndog9
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Thanks for the reply. A good summation of the posts I have read on the forum. It will be a busy day off Monday and will get back with homework done.

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 Posted: 05-15-2018 05:53 pm
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browndog9
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So, I am contacting the previous owner to get some more input and will get back.

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 Posted: 05-26-2018 08:00 pm
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browndog9
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Decided to remove distr. Easier than I had imagined. The distr was covered in fresh oil which may have been my problem. It has igniter in big bold letters. No mention of 2, so I bet it is capput because we left switch on often. I am going to send to store and get rebuilt with new igniter 2 and ballast coil. I am going to remove internal wire bAllast coming from tach. Any better plans or advice ?

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 Posted: 05-27-2018 05:58 pm
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Tom Bradley
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Engine oil is a good insulator, so oil on the outside of the distributor should not cause electrical problems. On the inside, however it could keep the spark from jumping the gap between the rotor and the electrical connections on the distributor cap. Either way, finding the source of the oil is a good idea.

Do I understand that you are sending out the distributor to have the Ignitor replaced? Replacing it is actually easier than removing and replacing the distributor. Certainly a do-it-yourself project.

The Ignitor 2 supposedly does not need any ballast resistance in the system. I have put about 5K miles on my car with an Ignitor 2 and no ballast resistor without any problems. Though I left the external resistor in place, but not wired in, just in case. If I were to keep a ballast resistor in the system, I would make it external rather than inside the coil. That way the ballast resistor is bypassed during cranking (assuming the original bypass wiring from the starter is still in place), which gives a hotter spark and faster starting up, especially when cold.

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 Posted: 05-28-2018 02:52 pm
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browndog9
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There was oil inside the distr and after looking at the history of the car, Thanks Mr Fox, it was a rebuild put on not so many miles back.
I figure it may be a bit wobbly and a good inspection of being true is in order.
New o rings and new bushing may slow new oil invasion.
So no ballast in coil and ditch the ni wire from the tach.
It looks like it is clamped in the wiring harness to a wire coming out of the tach. Should I get to the back of the tach and just remove the thing there. It has no sheilding for at least six inches, I have not cut the harness to inspect further.

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 Posted: 05-29-2018 05:31 am
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Tom Bradley
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I definitely would not leave any bare wires dangling around, especially since it is possible that the wire is shorted to some other wire inside the harness. If you want to make sure that the car can be returned to original configuration, then I would put some insulator around the wire. I have found that heat shrink tubing is very durable inside the engine compartment and can be slipped onto the wire and the shrunk down to a tight fit using a match or candle. Otherwise just cutting off the bare excess should be OK. Ballast resistors which can be attached to the coil mounting are inexpensive and readily available if going back that way is ever wanted.

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 Posted: 08-06-2018 02:09 am
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browndog9
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Well, I got the rebuilt dizzy back from Greg. It was equipped with a pertronix 2. With the help of my buddy we researched information on the site and got the car running again.
Words do not actually describe the joy of reading info a decade old that answers your questions and moves you down the line. This forum is a great treasure. I wish it was around in 72, when I bought my 59 MGA and started learning brit.

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 Posted: 08-07-2018 01:22 pm
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browndog9
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In my infinite stupidity I failed to thank the guys of the present tense who most definitely helped to solve the mechanical puzzle on which I was working/
Thanks to those who helped direct me to a starting car both past and present.

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