The V8 Owners Forum -

Afternoon all.

Been quiet for a while but thought id say hi.

Anywho....

Our Marcos is undergoing a rewire of the engine and dash electrics atm, but the ballast resistor on the side of the lucas Dizzy has thrown us a bit, as we cant for the life of us remember how its wired in??

If anyone could shed any light on the matter it would be great,

Many Thanks as always

Joe

Ballast resistor?, or ignition amplifier?

This is an ignition amplifier:



Chris.

If it is an amp you need to wire up, then the left terminal in the picture goes to the coil negative, and the right terminal goes to 12v ign live.
You also need 12v ign live to the coil positive terminal.

Regards Denis

Hello Joe, does this help at all?

http://www.vintagemodelairplane.com/pag ... ion01.html

Sorry ive been away for a while guys.

Thanks for the help, but that isnt the one.

It looks like a little rectangular beige or white block on the side of the dizzy, with maybe two or three pins. cant seem to find an image on the internet of it but ile know it as soon as i see it.

Hope this helps.
Many Thanks again

Joe

Hey Joe?

I don't recognise your description of what you think is a ballast resistor, and its also possible that your distributor is gonna be a stranger too.

Perhaps the best way would be to post some photos on the forum and let the audience hereabouts see what's going on.

Bear in mind that the word "ballast" resistor has been often mis-used and misunderstood in the context of Auto-electrics.

On ignition/starter systems it usually refers to a large resistor connected to the coil to limit the applied voltage when the engine is NOT cranking.

But it has also been used to describe the little resistor that protects an Efi ECU from voltage spikes or current surges occurring at Coil negative.

Then worse still, it has be totally mis-used to describe ignition amplifiers as you see from earlier queries on this thread.

To further clarify what you have are there any part numbers on your mystery component or the dizzy?

Ok Appologies.

Totally my fault here.

Seems my memory fails me sometimes.

The item im on about is on the side of the coil pack, the ignition amplifier can be seen in the background.



It seems quite simple but has the guy who is doing the rewire stumped for some reason.

Many thanks again and apologies for leading you down the wrong path.

Joe

With that ignition amplifier you don't need the ballast resistor.

Chris.

Ah ha! If you google for it you get loads of circuit images

Click this and then click on images

http://www.google.co.uk/search?q=ballas ... tor+wiring

This is one of them



Basically when the ignition switch is in the cranking position (4) and the engine is cranking, the battery voltage is a bit low at about 9 volts, so the 9 volt coil gets its voltage from directly from the switch.

Once the engine is running, and the ignition switch is in the ign position (3) the battery voltage recovers to about 12 volts so the coil gets its voltage via the ballast resistor causing the coil voltage to operate at approx 9 volts due about 3 volts being dropped by the resistor.

What the diagram does not show is the starter motor wiring.

I'm not familiar with your particular car electrics, hence the simple basic description.

However if you are using the ignition amplifier, I agree with Chris, the ballast resistor is not usually needed.

EXCEPT

Its possible that you have a 9 volt coil there, in which case the ballast resistor would be wired in series with the coil to prevent an electrical failure of either the coil or the amplifier or both.

thats the old 12v start 9v run system.... from the web .....

The ballast resisted ignition system was - I believe - developed by Ford when they were experiencing poor starting on a certain prodigiously used 4-cylinder engine. To get round the issue of the massive current drain caused by the starter motor functioning, the ballast-resisted system was designed. When you hit the starter button/key, a massive drop in available current to the coil occurs as the starter motor does its thing. The colder the weather or the more worn the starter motor, the more current it draws, the less there is passed to the coil to instigate ignition.

The ballast-resisted system utilises a 6 (commonly called the 'cold start' system) or 9-volt coil instead of the older style 12-volt item. When you hit the starter button/key, the coil is still seeing maximum current so produces a nice, big, fat, 12-volt induced spark to start the engine. Kind of 'super-charging' the coil by increasing the voltage to way above it's normal supply - by some 30%+. When the key is released, the ballast resister ensures the voltage passed to the coil stays at 6 or 9 volts. It also significantly increases points life by massively reducing the EMF contained in the system when the points trigger the ignition system (the spark you see at the points when the open) and therefore the intensity of the 'arc' across the points.

Running a 12-volt coil on a ballast-resisted system will produce a very weak spark - consequently the engine won't run too well. Running a 6 or 9-volt coil on a 12-volt system will produce a healthier spark but will burn the coil out real quick. I messed about with this years ago on my Miglia motor and found a few extra horses when using a 9-volt coil on a 12-volt system, but coil failure was way too rapid to make it economically viable and coil failure time was not pre-determinable so could leave you high and dry in the middle of a race!

Identifying which system your car has is pretty straightforward - I believe generally all Minis from 1984 onwards were fitted with ballast-resisted ignition systems. Identifying if it is ballasted resisted became very much easier on later post-1990 cars as the system used a resisted wire rather than an actual resistor electronic component. The ballasted resisted wire is coloured pink with a green tracer in it and is connected to the coil in place of the old, original white wire. However, the ballast-resistor component equipped models still used the white ignition feed wire to the coil that actually ran the 6-volt coil system. The only truly definite way of discovering which your car has is by testing the voltage at the coil lead feed with the ignition on. 12-volt says it's the old system, 9-volt identifies it as ballast-resisted, 6-volt as the older 'cold start' set-up.

And you must use the correct electronic ignition system to suit your wiring system - otherwise it'll get real expensive to keep replacing blown electronic ignition kits!
http://www.calverst.com/articles/EL-Ign ... ystems.htm

All good comments.

That ignition amplifier was never used with a ballast resistor. However, if you have the wrong coil, it might help. But I would just get a coil that you know is the right one.

Chris.

ChrisJC wrote:it might help.

Oh, Come on Chris!, With so little and misleading information, we are all guessing here, but truly, adding a ballast resistor will allow the 12 volt amplifier switched system to generate a usable spark from a 9 volt coil.

From the information given so far, one had to assume that the resistor was once included on this car, jury rigged into the ignition circuit somehow.

The amplifier would not know or care if it was switching a 12 volt coil, or a 9 volt coil with ballast resistor or a 6 volt coil with two ballast resistors.

Mind you, the tacho and/or an ECU might be confused by an unusually low signal from coil negative.

Must say guys, thanks soo much for the amazingly deep description.

I have no reason to question, if the coil is the correct for this car, or whether the resistor was added afterwards or not due to the car running very well before the rebuild began with everything hooked up.

Many Thanks again gents, tis greatly appreciated.

joe

jomeo wrote:Must say guys, thanks soo much for the amazingly deep description.

I have no reason to question, if the coil is the correct for this car, or whether the resistor was added afterwards or not due to the car running very well before the rebuild began with everything hooked up.

Many Thanks again gents, tis greatly appreciated.

joe

Some after market electronic ignition systems do need an external dropper resistor. The Mallory Unalite dizzy is one. However, this is more just to limit the maximum current flow and prolong life.

The Lucas DLM dizzy doesn't. But you do need the correct coil for best performance. It's not worth messing about with the wrong coil and resistors - unless you have the sophisticated test equipment to check the actual spark.

JSF55 wrote:
[snip]

The ballast-resisted system utilises a 6 (commonly called the 'cold start' system) or 9-volt coil instead of the older style 12-volt item. When you hit the starter button/key, the coil is still seeing maximum current so produces a nice, big, fat, 12-volt induced spark to start the engine. Kind of 'super-charging' the coil by increasing the voltage to way above it's normal supply - by some 30%+.

[snip]

That's rather misleading. The purpose of the dropper resistor and low voltage coil is to produce the same spark when cranking as when running. In other words, to get round the battery voltage drop caused by the use of the starter motor.