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Old 04-17-2019, 10:18 PM   #1
50fordcoupeman
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Default Ballast resistor needed??

It is my understanding that a ballast resistor helps the points not to burn so they were added when Ford went from 6V to 12V. My question is is a ballast resistor needed with an electronic ignition installation?

Thanks!!
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Old 04-17-2019, 11:25 PM   #2
Daves55Sedan
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Default Re: Ballast resistor needed??

The manufacturers installation instructions for the electronic ignition equipment should tell you if you need the resistor or not. Example; the papers that were included with the pertronix ignition that I had received, did include that information.
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Old 04-17-2019, 11:47 PM   #3
slumlord44
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Default Re: Ballast resistor needed??

Pertronix says not to use the resistor. Have the second one in the TBird and just installed one in my '65 Mustang with Hi Po distributor.
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Old 04-18-2019, 11:19 AM   #4
39deluxecp
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Default Re: Ballast resistor needed??

no resistor with Ford Dura spark or any other electronic ignition is used
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Old 04-18-2019, 11:46 AM   #5
50fordcoupeman
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Default Re: Ballast resistor needed??

The resistor in question is on a 1971 Ford 302. The engine runs very good as is. The pertronix was installed when I got the car so no instructions but the apparently original ballast resistor is still wired in.
Do I simply bypass the resistor by connecting the 2 wires together that are hooked up to that resistor?
Thanks for everyones help!
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Old 04-18-2019, 11:50 AM   #6
V8 Bob
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Default Re: Ballast resistor needed??

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Quote:
Originally Posted by 50fordcoupeman View Post
It is my understanding that a ballast resistor helps the points not to burn so they were added when Ford went from 6V to 12V. My question is is a ballast resistor needed with an electronic ignition installation?

Thanks!!

It really depends on the electronic ignition and coil you're using. I'm not sure about OE, but aftermarket Pertronix states no resistor when using their matching coils, while Mallory used to offer some coils that required a resistor, some did not, depending on internal resistance.
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Old 04-18-2019, 12:32 PM   #7
Flathead Fever
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Default Re: Ballast resistor needed??

The type of coil determines if you need a resister or not. Some coils have built in internal resistors and some use external resistors. Sometimes the coil are stamped "internal resistor". If you run a coil designed for a ballast resistor on straight 12 volts it will burn up the wiring inside the coil in a short time, probably within a couple of days. The internal windings in the coil are made from really thin wire. They can handle 12 volts for only a short period of time, like when cranking the engine when the ballast resistor is by-passed for a hotter spark.
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Old 04-18-2019, 12:53 PM   #8
50fordcoupeman
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Default Re: Ballast resistor needed??

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Originally Posted by Flathead Fever View Post
The type of coil determines if you need a resister or not. Some coils have built in internal resistors and some use external resistors. Sometimes the coil are stamped "internal resistor". If you run a coil designed for a ballast resistor on straight 12 volts it will burn up the wiring inside the coil in a short time, probably within a couple of days. The internal windings in the coil are made from really thin wire. They can handle 12 volts for only a short period of time, like when cranking the engine when the ballast resistor is by-passed for a hotter spark.
Thanks flathead. I was just out in the shop and loosened the coil enough to spin it around. It says to use an ext resistor on it. This set up has approx 2000 miles in 3 years on it with no problem. I guess if isn't broken...................
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Old 04-18-2019, 12:57 PM   #9
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Default Re: Ballast resistor needed??

All coils have a fine winding primary coil but they vary in resistance values depending on the application. Many of the early coils used by Ford in the 6-volt era were not designed to be able to take much heat so Ford used a ballast resistor to control the current to the coil to reduce internal heat build up. When Ford went back to the can type design in the 8BA era, it could take more heat so no ballast was necessary. When the cars changed over to 12-volt in the mid to late 50s, the ballast had to come back.

Coil technology started to change in the 1960s when more and more electronic ignition systems started to show up. Coils were manufactured with newer materials that could take more heat while still maintaining reliability. Most of the later coils will have 12-volt marked on the body indicating that they can be run without a ballast. Electronic ignitions started to use higher resistance values for their primary coils in order to get a hotter spark. There are advantages to having a breaker-less ignition and one is no breaker points or condenser to wear out. The other is a much hotter spark. The components have to be well matched to get any reliability though.

I would use what ever coil the ignition system manufacturer recommends or their will be problems. If you do that and it is still suffering from reliability problems then it is time to change to a different system. Pertronics should have information about their systems on line. If they don't then I would question even using their product or I would update to one of their systems that does have better info.
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Old 04-18-2019, 04:10 PM   #10
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Default Re: Ballast resistor needed??

Quote:
Originally Posted by 50fordcoupeman View Post
Thanks flathead. I was just out in the shop and loosened the coil enough to spin it around. It says to use an ext resistor on it. This set up has approx 2000 miles in 3 years on it with no problem. I guess if isn't broken...................
It really should have resistor on it or the coil will burnout. I worked for the phone for 30-year's as a fleet mechanic. We had Dodges that had external ceramic resistors on them. They burned out all the time. I could tell the resistor was bad because the engine would start while you were cranking (resistor is by-passed while cranking) and then the engine would quit as soon as you released the key. They have a certain resistance value to them but I always found it difficult to check them with a ohm meter because the measurement changed so much with the temperature of the resistor. They were almost always either good or they didn't work at all so there was no reason to stick an ohm meter on them.

One day I had a resister burnout and I did have one in stock. I bypassed the resistor thinking it would be okay for just a day until the new resistor arrived. The truck came in on the tow truck the very next day with a burned out coil. I never did that again. I have hundreds of those kinds of lessons I learned while experimenting on phone company vehicles.

There are two kinds of external resistors. Dodge used the ceramic one bolted in the engine compartment. Ford used a length of resistor wire under the dash, I think it was pink? Its best to put a volt meter on the positive wire to the coil. Disconnect it from the coil and check it with the key on and see what voltage you have. If you left the wire hooked up and the circuit was energized (key on and points closed) and you tried to check it you would be performing a "voltage drop test" which locates resistance in the circuit and not the available voltage.

Last edited by Flathead Fever; 04-18-2019 at 04:26 PM.
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Old 04-18-2019, 04:50 PM   #11
50fordcoupeman
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Default Re: Ballast resistor needed??

Quote:
Originally Posted by Flathead Fever View Post
It really should have resistor on it or the coil will burnout. I worked for the phone for 30-year's as a fleet mechanic. We had Dodges that had external ceramic resistors on them. They burned out all the time. I could tell the resistor was bad because the engine would start while you were cranking (resistor is by-passed while cranking) and then the engine would quit as soon as you released the key. They have a certain resistance value to them but I always found it difficult to check them with a ohm meter because the measurement changed so much with the temperature of the resistor. They were almost always either good or they didn't work at all so there was no reason to stick an ohm meter on them.

One day I had a resister burnout and I did have one in stock. I bypassed the resistor thinking it would be okay for just a day until the new resistor arrived. The truck came in on the tow truck the very next day with a burned out coil. I never did that again. I have hundreds of those kinds of lessons I learned while experimenting on phone company vehicles.

There are two kinds of external resistors. Dodge used the ceramic one bolted in the engine compartment. Ford used a length of resistor wire under the dash, I think it was pink? Its best to put a volt meter on the positive wire to the coil. Disconnect it from the coil and check it with the key on and see what voltage you have. If you left the wire hooked up and the circuit was energized (key on and points closed) and you tried to check it you would be performing a "voltage drop test" which locates resistance in the circuit and not the available voltage.

Thank you flathead. Maybe who ever did this work knew what they were doing..............I will leave it alone!
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Old 04-18-2019, 05:12 PM   #12
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Default Re: Ballast resistor needed??

We use to have a Standard products illustrated ignition book at work. It showed a picture of very type of points, coils and resistors. It gave your the resistance of the resistor. I went online to find that catalog. The online catalog shows you a picture abut when you click on description it tells you how popular it is and how much shelf space it takes up but not a thing bout the part. Everything is setup now to enter the year and make of car and a part number pops out. But when your modifying stuff you can't do that. You need the old catalogs which I kept. Every year we got new catalogs at work and every year I took the old ones home and updated my collection.

To give you an idea here is a page from the on-line coil resistors. In the 1980s catalog it would have told you if the coil had an internal or external resistor. It might have told you which of these resistors went with each coil. It would have told you the resistance value of each of these resistors. Half of these resistors could all be the same resistance and they just mount differently. Computers have not yet replaced books in the world I live in.

https://www.standardbrand.com/en/eca...ype=p&search=s
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Old 04-19-2019, 05:09 PM   #13
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Default Re: Ballast resistor needed??

Most of the old ballast resistors were 1.3 to 1.5 ohms. The coils were mostly 1.5 ohm primary until they wanted to eliminate the ballast. Some of these new electronic types are 3 ohm primary.

Modern cars are triggered by the computer and have a coil for each cylinder but the induction coils still work pretty much the same way they always have except they throw a hotter spark across a wider gap.
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Old 04-20-2019, 09:51 AM   #14
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Lightbulb Re: Ballast resistor needed??

okay, while we are talking coils, can some one explain to me what the difference is in coils with different oums? Is a higher ohm better for more spark? what is the difference.thanks
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Old 04-20-2019, 10:57 AM   #15
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Default Re: Ballast resistor needed??

Less ohms is a hotter coil. A v8 needs about 3-3.5 ohms resistance on points to keep from burning points rapidly. You can use a coil with this resistance and no ballast resistor. Or you can use a a coil of about 1.5 ohms and a about a 1.5 ballast. The advantage of using the ballast set-up is that you can bypass the the ballast at start-up for hotter spark when cranking and revert to ballasted voltage to run. There is a terminal on most solenoids for the bypass.

Electronic ignitions are built for a given ohm coil. Pertronix tech told me that you can run more resistance at the expense of high rpm performance. Too little resistance will burn the electronic unit.
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Old 04-20-2019, 12:33 PM   #16
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Default Re: Ballast resistor needed??

I discovered a petronix unit inside my T-Bird distributor. How durable are they?



The vacuum line wasn't hooked up, the carb/manifold vacuum fittings were intentionally plugged. I'd read that some petronix units need the vacuum advance. What's up with that?
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Old 04-21-2019, 12:07 AM   #17
50fordcoupeman
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Default Re: Ballast resistor needed??

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I discovered a petronix unit inside my T-Bird distributor. How durable are they?



The vacuum line wasn't hooked up, the carb/manifold vacuum fittings were intentionally plugged. I'd read that some petronix units need the vacuum advance. What's up with that?
My pertronix is installed on 1971 302. It has been there about 4 yrs without a hiccup. The vacuum advance is connected.

How well does yours run the way it is hooked up?
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Old 04-21-2019, 02:31 AM   #18
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How well does yours run the way it is hooked up?

I've not put more than a few miles on the car since I bought it. It came with the dist. vacuum advance disconnected. I thought "Huh?" Then I saw the that the vacuum source inlet fittings it might connect to were all intentionally plugged, and I wondered if it might be an electronic ignition. It was. But then I read that Pertronix usually still uses the vacuum advance.



I checked the shop manual to find which vacuum inlet fitting it would use and hooked it up to that. To be honest with you, I don't know that I can tell a major difference in how the car ran with the vacuum disconnected vs. now - even ast speed - but when I put the dwell meter on (before I knew it was electronic ignition) with the advance disconnected, it read about 16 degrees dwell , as I recall, which isn't correct for that engine. With the vacuum connected it read 28 degrees, which is what the manual said that a points ignition should be, but I don't know how pertinent that is with an electronic ignition.



With the vacuum connected, the car generally runs pretty smooth, but has moments of less than smooth idle that seem to come and go suddenly. I don't think it has the Pertronix coil on it.
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Old 04-21-2019, 01:24 PM   #19
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Default Re: Ballast resistor needed??

JimNNN, you really should to start a new thread. When mixing different cars and engines, it gets confusing. You mention a T-bird distributor but there are different engines and distributors in T-bird cars over the years of production. We don't know what year or what engine you have. All cars with built with vacuum controlled spark timing benefit from a working system whether the beaker is a set of beaker points or an electronic form of trigger.
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