Which coil?

[Staggering About]

At the weekend I was helping a friend locate a problem he has with power loss under load. I swapped our coils over and discovered that they are both 12V coils. As they should be 6V, what difference does this make to the running of the engine? Mine has always run well with this coil. I do have the Pink/White resistor wire.
Should I change it for a 6V coil?
Thanks.
Alan

[SGN]

Hi Alan
have a read here, http://www.ldparts.co.uk/shop/shop.p...336275ded82b5a

Cheers
Steve

[Staggering About]

Thanks Steve. I don't have sports electronic ignition but that explains a lot.

[SGN]

He give the same write up with his standard coil.

[Staggering About]

So it does & I may go that way. My question is, what is the performance of a 12V coil with a 6V feed? I assume that it gives a poorer spark. Is that correct?

[ChasR]

That is how I understand it, yes. Of course, if the situation is reversed you will get a better spark, at the expense of points life and potentially coil life (overheating the coil).

You say your coils say 12V on them, does it mention anything about a ballast resistor on them. The standard issue GCL334 sold by many specialists now is sold as a 12V ballast coil.

If they are 12V coils designed to work without a ballast resistor I would check what voltage you get at the coil terminals with the ignition on and the engine off (Don't leave the ignition on for too long). It should be around 6 volts with the presence of a ballast resistor .

[Staggering About]

There's nothing on the coil to say anything about a resistor. I've had the car for 10 years and this is the first time that I've had the coil off.
I'll test the voltage tomorrow.

[Guest]

If you have a 12 volt coil and a ballast resistor, then the coil will only see 6 volts and your spark is bound to be weaker - by how much I do not know. However, as you have been happily running like that for 10 years, it does not sound much of a problem. If you check the voltage at the coil and it is 6 ish, then I would buy a 6 volt coil and see what difference it makes. I'll bet that it will liven the car up. Vmad's method of measuring the coil voltage is easier - take off the coil -ve connections and ground the coil -ve. Switch on and measure the voltage at the coil +ve.

I had the opposite issue. I have a 6 volt coil and the wiring ballast resistor (only recently learned all this). When someone fitted Lumenition, they also fitted the ballast resistor than came with the kit. So I had 2 resistors in series with the coil, so it was only seeing about 3 volts in normal runnind about 4.5 on cranking. The car had been running for years like that and it was only when troubleshooting the hot starting problem that I discovered it. Now with the Lumenition resistor shorted out, the car fires up instantaneously hot or cold.

[V Mad]

I have noticed that even companies who specialise in selling ignition systems often do not know the technicalities of what they sell. Their tech literature is not self explanatory and when you phone for clarification you may not get a clear answer, or you may even get a wrong answer!

The main confusion seems to be for example what is meant by a "12 volt" or a "6 volt" coil. The question we need to ask is whether it is a ballast type coil or not. A 12 volt coil could be a ballasted coil that runs on a typical car 12 volt system (as opposed to a 24v or 6volt). Alternatively it could be called a 6 volt coil because the ballast drops the voltage to 6 volts. Its not clear which type they are selling.

Another way to check which one you are getting is that a ballasted coil (that runs on a 12 volt system) usually has a resistance of 1.5 ohms, whereas an ordinary non-ballasted coil has a resistance of 3 ohms. Whichever you use, ballasted or non-ballasted, the total resistance in either type is about 3 ohms which gives a current of 4 amps (12/3).These 3 ohm systems are for use with points, and a few popular electronic systems.

The exception to this is where you have a high end electronic ignition system that can take a higher peak current, and in these systems, no ballast is used, and a special low resistance coil is used (resistance is around 1.5 ohms). These systems should make it quite clear that they can run with a low resistance coil.

In summary you will have one of two types of system:
1.Points or popular types of electronic ignition running a ballast coil with ballast resistor
2. High performance elec ignition running with no ballast and a special coil.

NOTE: All stags should run on a ballasted system, however some stags may have been modified so the ballast may have been bypassed. In this case, it will not run as well unless a high end electronic system has been properly installed.

I hope that's not too confusing.
Cheers

[singapore stag]

To Ballast or not to Ballast that is the question chris..

Sukh.

[Motorcycle mad]

The issue of a 12volt coil is a very confusing one, When Lucas were manufacturing in the UK they use to stamp on the bottom of the coil a code number, if it was for use on a 12 volt system (with or without a resistor) the coil it would be stamped 12 followed by two letters and another number, the letters and last number told if it were a straight 12 volt coil, or a 12volt coil to be used with a resistor, unfortunately I don’t remember the codes now.

I think the problem we now have is that owners are looking at their Lucas coils not understanding the Lucas code system and assuming they are a full 12 volt coil, when in fact they should be used with a resistor of some sort, whether it be a ceramic resistor as on the Mk1, or the pink and white resistive wire built into the wiring harness as on the Mk2, again on the Mk 2 some owners do not understand there is a piece of resistive wire built into the harness. All voltage tests must be carried out with the coil under load, not on open circuit otherwise you will get a 12-volt reading.

Regarding the currant replacement market, I just don’t know anything about the modern coil, you should seek the advice of a good supplier/auto-electricians.

Ken

[Staggering About]

Well I've had a look at my coil again. It is a Remy Delco 7992190 and seems to be the one recommended for the Stag. I've tested it and it is 1.5 ohms. I tested the voltage as suggested and it is 6V.
I am using a Newtronics electronic ignition.
I have a spare coil. It is a Lucas DLB102. The measurements are the same.
It looks as though I'll have to find something else to find fault with.
Thanks to you all for your input.
Alan.