What model coil is that? May say on the bottom, may also say either 6V or 12V.
A related question:
What the heck does the ballast do? I’ve had two 69 E-types, neither of which had one so I’m not all that familiar with them.
Also, they seem to cause a lot of problems. Is it possible to just eliminate the ballast from the ignition system?
Like I said, I don’t have one so I’m just asking out of curiosity.
Geo, no markings on the bottom of the coil. I don’t know what model of Lucas this is.
Bob
John,
That is a great question. My guess it had something to do with all of the other changes made due to USA regulations on emissions…
Hopefully someone else that knows can jump in.
I would love to eliminate that ballast if its not needed. Also, and especially if it fixes the tach issue.
Thanks,
Bob
I installed a Pertonix distributor on my Series II and have had absolutely zero problems with the tach. As I said, no Ballast to fool with.
Replacing the points distributor with Pertronix and removing the ballast would fix the tach issue?
Bob
Bob - It looks like the most commonly sold Lucas Sport Coil - DLB105 - which does not need and should not have an external ballast resistor.
The ballast set-up provides more voltage to the coil during engine cranking but requires a different coil than non-ballasted systems.
The test to see which coil is it (and if it needs a ballast) is to measure the resistance across the terminals.
About 3 ohms is correct for a system w/o a ballast (like a 69 S2). About 1.5 ohms is a coil that needs an external ballast resistor
Hi Geo, thanks!
I will eliminate the ballast from the equation and see what happens. Will let you and others know the outcome. Thanks! Bob
So I can remove the white/blue wire going to the ballast. When I unplug the 2 white wires from the ballast, where do these then get plugged in?
Thanks, Bob
I never had a ballast resistor on my car so I can’t say that. I’m just noting that on my car which didn’t have the resistor I had no tach problems when I installed the Petronix.
As far as I know I have no ballast resistor on my Feb 1968 car. I have a Pertronix module inside my stock distributor for many years now. Tach has always worked fine except for when the ignition switch fried and melted the white wire that loops on the back of the tach. Once I replaced that wire it took me some fiddling to get the tach to respond again but 10+ more years later it continues to be fine. Below is link to the 1.5 wire diagram. Is it perhaps possible to bypass the ballast resistor safely to see what happens ? Like John I do not know what the ballast does.
David
68 E-type FHC
Bob,
If you really have two wires on that side of the ballast resistor and one goes to the tach and the other goes directly to the ignition switch, then you have not wired it correctly. If you look at the circuit diagram provided by MGCJAG you will see only one white wire which goes to the tach, and having passed through the tach it goes on to the ignition switch. If you have added a second white wire directly from the ballast to the ignition switch (bypassing the tach), that is not correct. As for the question of the need or lack of need for the ballast resistor, you really need to determine what coil you have. Measure the primary resistance of the coil (between the + and - terminals). If it is around 3.0 ohms, you do no need a ballast resistor. If it is around 1.5 ohms, it is designed to work with a ballast resistor, and will overheat if you don’t use one. Rather than just moving wires around, and “trying things”, I’d really encourage you to be systematic and (a) determine what components you’ve got, and (b) make sure that are wired up according to the wiring diagram. The ignition system is really very simple…
I had Nissonger redo this tach with modern electronics. Will work with both standard points distributor and also newer electronic distributors (Pertronix). Nissongers instructions are to run a new white wire from the tach directly to the ballast. The green wire from the tach goes to the fuse block.
Bob
Bob,
Thanks for the explanation - I guess I must have missed it when you explained this before?. Sounds like you should ask Nisonger to debug the tach then, because they’ve asked you to change the conventional wiring. I can’t count how many times a problem reported by a fellow lister has ended up being due to something non-standard that was fitted (and often not mentioned…). Good luck.
-David
John, to my understanding… a ballast resistor ignition is, to a large degree, a choice the engineers make. Some choose to use one, some choose not to. Firstly, an ignition system is a “matched” system. The coil, the ballast resistor if used, the capacitor, the ignition wires, and the spark plugs are all matched to suit each other. Changing any arbitrarily, as people often do, is often not an advantage. (Example, Some feel copper plug wires are always better.).
So, as many do know the coil and the ballast resistor much be matched, which of course means if the coil is designed for a ballast resistor, that coil should not be used without it, and vice versa. Also, as said, typically a ballast resistor is by passed while the engine is cranking. Thus full battery voltage (which is pulled down while cranking, will be applied to the coil while cranking, and then the ballast resistor reduces the running voltage (14+) while running. But not only that, this is called a “ballast” resistor which indicates more. In this case, as the engine rpms vary, so does the current through the resistor, which causes the resistor to change temperature with rpms, and thus resistance changes with rpms, thus it becomes an automatic regulator to the coil. Why did I start by saying it is a choice. It almost seems that through history, designers chose one over the other at random. Even within a brand, some engines would use one type, and another engine would use the other. If one system has clear advantages, I have not heard.
Tom
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Thanks Tom, good stuff.
I did a bit of research since I asked and from what I see a ballast resistor helps points last longer and isn’t necessary with an electronic ignition.
John, Again a choice. If I remember, both early Chrysler and Mercedes electronic ignition systems did use ballast resistors. And many systems without ballast resistors still got very good point life.
Tom
When the engine is cranking, there is the heaviest load on the battery. So, for example any other load like the radio or the lights are starved and radio goes quiet or headlights go dim. The ignition circuit is no different and can end up with much less than 12 V if the battery is tired. This can obviously cause poor starting, because the coil would prefer 12 V.
Ballast ignitions therefore use coils rated below 12V - say 6 or 9V - which work fine while cranking, even on the leaner mixtures introduced at the time. Starting issue solved.
The problem now is that once the engine is running, there’s no huge cranking drain and the 6 or 9V coils can only run temporarily on full 12-14V before they overheat. The solution is to wire the ignition so that during cranking the coil gets a direct ‘12V’ feed but when the key is releases and goes back to Run instead of Start, the direcf feed is disconnected and a second feed is used which includes the ballast resistor. That feed drops the voltage and protects the lower volts coil.
That’s it… but I think Bob still needs to identify what coil he has – 6V or 12V. The resistance test should tell him that.
Geo, I will test the resistance after church today. More to come. Thanks for everyone’s input. Happy Easter, Bob