Ignition wiring puzzle

[Davo1805NZ]

Hi guys,

Just seeking some advice regarding wiring connections as I move towards first startup. I'm using the coil and Lumenition system which were on the car (running) before I pulled it apart - the only new item in the mix is the main wiring loom (RKC778 purchased from Rimmers). Things that have me scratching my head are as follows -

• The two wires in the new loom which connect to the + terminal on the coil are white/yellow & pink, but the wiring diagram says the latter (ballast wire) should be pink/white.
• The coil - according to the label on it - is a Lucas LD110, which according to info I found on the web is a 12V coil with 1.5 ohm primary resistance, yet when I meter across the terminals I get 2.7 ohms.

I'm worried that the new loom is different from that which was removed, and is perhaps not compatible with the other components. I'd be grateful if somebody can clarify for me, or perhaps advise some checks that I can make to establish what I have. Thanks in advance.

Dave

Coil.jpg

[Phil S]

If you are running a 12v coil and luminition you have no need of the balast resistor as the set up gives a better spark.
you need to trace where the other end of the wires in question go to decide if they need to be connected or isolated

[marshman]

The DLB110 is a coil requiring a ballast and the primary winding should read around 1.5 Ohms.

Are you sure you measured it correctly? Did you put the test leads together and note the reading then subtract this from the reading across the terminals. It is notoriously difficult to accurately measure low resistances and the test leads can have a significant resistance themselves. Worth double checking - even a bit of dirt/tarnishing on the terminals can have a big effect on the reading.

Roger

[Davo1805NZ]

Ha... a trap for young players - no, Roger, I didn’t do that; never thought about the resistance in the leads. Will re-check and see what I get. Cheers.

[jbuckl]

Imho the ballast system still gives a quicker fire up.
the coil voltage is reduced during cranking, so it’s worth to keep it if you’d like a quick to fire up start.
the pink & white wire (resisted) may no longer be available for new looms.
I replaced the one on my car, think I could only get a length in pink at the time.
fwiw the Lucas dlb coil I bought wasn’t very good.
currently running a Bosch red coil.
also recommend a viper dry coil.
my engine appears/sounds to fire after less than one turn of the engine from cold...all compressions are above 150 psi.

[jbuckl]

Imho the ballast system still gives a quicker fire up.
the coil voltage is reduced during cranking, so it’s worth to keep it if you’d like a quick to fire up start.
the pink & white wire (resisted) may now longer be available for new looms.
I replaced the one on my car, think I could only get a length in pink at the time & the supplier said they only had a small amount left at the time.
I tried a Lucas dlb....wasn’t that good.
currently using a ballasted Bosch red coil.
good results with a viper dry coil too.
my engine appears/ sounds to fire on less than 1 turn of the crank, with all compressions over 150 psi.

[Davo1805NZ]

OK, so per Roger's response above, I read the meter with its leads shorted together and saw 1.3 ohms, indicating a net figure for the coil of 1.4 ohms - so I guess that solves that part of the puzzle for me.

However, I'm still unsure about the wiring to the + terminal on the coil. I have read the info. in the ROM section 86.35.00 and my understanding is that the purpose of the ballast resistor (or resistor wire) is to reduce the voltage supplied to the 6V coil during normal running. During starting the ballast resistor is bypassed by the white/yellow wire, which delivers 12V to the coil from the IGN terminal on the solenoid. Given that my coil is 12V it would seem to me that if ballast resistance is present, then during normal running the coil would not be getting enough voltage? On the wiring diagram the ballast resistor wire appears to terminate in a connection (somewhere?) to a white wire which goes to terminal 19 on the fuse box. I metered between the end of the pink wire and terminal 19 and saw a reading of 2.7 ohms which, again allowing for resistance of the test leads, would indicate a net resistance of 1.4 ohms, which concurs with what the ROM says. The conclusion I arrive at is that I will need to bypass the ballast resistor wire in order to provide full voltage to the coil during normal running. Do I have this correct? If so, I'm wondering how to bypass the ballast - can anybody tell me where the transition occurs between the ballast resistor wire and the normal white wire? Thanks in advance.

Dave


Ballast.jpg

[KOY 23]

Don’t bypass the ballast. The marking on coils can be unclear, particularly as Lucas parts are rebranded now.
What they mean is that it’s intended for use on a 12v system but omit today with a ballast resistor.

[DJT]

https://www.holden.co.uk/p/lucas_12_volt_sports_coil_for_use_with_ballast_resistor

High output 12 volt Lucas Sports coil for use with a ballast resistor. This coil has a push-in centre lead. Supplied with the mounting bracket and is ready to fit. Wires attached via 5mm ring terminals, or adaptors (included) to take Lucar terminals Primary coil resistance 1.5 ohms and secondary coil resistance 8.6 k/ohms. DLB110. A standard type coil is also available for use with a ballast resistor.

[mole42]

good results with a viper dry coil too.
my engine appears/ sounds to fire on less than 1 turn of the crank.

I'll second the Viper coil, bought mine at the last Stoneleigh. The engine starts after one turn of the crank every time at the moment, and I'm not using it every day like I was in 2019....

[marshman]

OK, so per Roger's response above, I read the meter with its leads shorted together and saw 1.3 ohms, indicating a net figure for the coil of 1.4 ohms - so I guess that solves that part of the puzzle for me.

However, I'm still unsure about the wiring to the + terminal on the coil. I have read the info. in the ROM section 86.35.00 and my understanding is that the purpose of the ballast resistor (or resistor wire) is to reduce the voltage supplied to the 6V coil during normal running. During starting the ballast resistor is bypassed by the white/yellow wire, which delivers 12V to the coil from the IGN terminal on the solenoid. Given that my coil is 12V it would seem to me that if ballast resistance is present, then during normal running the coil would not be getting enough voltage? On the wiring diagram the ballast resistor wire appears to terminate in a connection (somewhere?) to a white wire which goes to terminal 19 on the fuse box. I metered between the end of the pink wire and terminal 19 and saw a reading of 2.7 ohms which, again allowing for resistance of the test leads, would indicate a net resistance of 1.4 ohms, which concurs with what the ROM says. The conclusion I arrive at is that I will need to bypass the ballast resistor wire in order to provide full voltage to the coil during normal running. Do I have this correct? If so, I'm wondering how to bypass the ballast - can anybody tell me where the transition occurs between the ballast resistor wire and the normal white wire? Thanks in advance.

Dave


Ballast.jpg

As both John (Koy23) and Dave (DJT) have said the DLB110 DOES NEED THE BALLAST. The labelling is confusing and in some respects misleading. As John said it is not a 12V coil but a coil for a 12V system WITH Ballast.

You have confirmed the ballast resistance at around 1.4 - 1.5 Ohms and also the coil resistance to be the same (1.5 Ohms). This gives a total around 3 Ohms. Using good old Mr Ohm and his law you get a nominal static (non - running) current of around 4A on a nominal 12V supply. Which is correct. Remove the ballast and the current will double to around 8A and your coil will quickly over heat and die.

Real 12V coils that do not need a ballast have a resistance in the region of 3 Ohms (maybe slightly less) so still giving a "static" current of 4A but without the ballast.

As an aside, the "power" lost or dissipated in the ballast resistor is going to be upto 4A x 6V = 24W, (actually less than this when the engine is running) OK for the early external resistor mounted on the coil as it is in free air and can lose this heat easily, but quite a lot of heat/warmth to be dissipated by the pink "resistance" wire snuggly wrapped in the loom. It is this constant heat dissipation that can lead to the eventual demise/failure of the resistance wire in the loom - especially if some previous owner has tidied up his loom and wrapped a load of loom/insulation tape around it so that it gets even hotter.

To my way of thinking a ballasted coil should run cooler as it is only dissipating a maximum of 24W - (6V x 4A) where as a 12 V coil is dissipating twice this at 48W - (12V x 4A). (NOTE: they are both static figures with the engine not running, under running conditions the average power dissipation is less). Not really thought about it before but it must make a difference to running temperatures and hence life of the coil - an argument to stick with the original ballasted system?

Sorry for the longish ramble but got carried away with my thought train

Roger

[Davo1805NZ]

Thanks for all the responses & clarification - I guess I can stop worrying and get on with it now!

Cheers

[DZP]

Hi Dave,
I fitted a new loom to my MK 1 Stag after purchase, because the ignition circuit wiring had overheated and some of the white wires had melted.
I think this was caused by incorrect wiring of a MK II tacho and no ballast resistor with a ballast coil.
I have Powerspark electronic ignition fitted and Simon has a good FAQ telling you how to identify if you have a ballast resistor fitted, but you will need use your voltmeter.

https://simonbbc.com/faq-fitting-how-to/

I have a ballast resistor and 1.5ohm ballast coil, the Lucas DLB110.
My coil isn't getting the 12v feed from the starter solenoid during cranking, so it takes maybe 6 or 8 turn of the engine before it starts for the first time when cold.
I am going to take a look at this today, but I expect it's a burnt contact inside the solenoid,
It looks like you have:-
A pink resistor wire with 1.5ohm resistance, which is correct.
A Lucas ballast coil with 1.5ohm resistance, which is correct.
So, ONLY when you crank the engine should you get 12v fed to the +ve terminal of the coil for cold starting,
If you do not get this, then check that you have a wire from the Starter solenoid to the coil and this provides 12v during cranking, if it doesn't you have a similar issue to me.
I hope that helps,
Den

[jbuckl]

You can run either a 1.5 or 3 ohm coil on a mk1 or mk2.
starting & coil life will be affected if the cranking and running voltage doesn’t match the coil.
also, most electronic ignition systems need a 12v feed & won’t work well with a feed taken from a ballasted or other non stable feed.
the ballast system helps starting as when cranking the system voltage is reduced, that is true for both points & electronic ignition.