Wiring coil and ballast resistor

[JohnFol]

Morning all, just taken delivery of a new coil and was about to connect it when spotted something not right with the ballast wiring. 1st picture was taken before I started playing with things and yes, the resistor does appear to be neither in parallel or series with the coil (I've super imposed the wires as they run under the coil but they both join on the +ve terminal)

2nd photo is the Lancia owners book showing the wiring (37 - resistor, 28 - coil) however I hear they do not always match reality. For completeness, Haynes doesn't show the resistor at all!

So, for an electronic ignition, carb spyder, should I rewire to match the Lancia diagram or is there a better guide out there?

[JohnFol]

And the Lancia owners book's wiring diagram

[peteracs]

Hi John

Haynes only has pre facelift and hence pre electronic ignition diagrams if I remember correctly, so no ballast resistors.

I guess my question is, why is there a ballast resistor in the first place, maybe to limit current through the electronic ignition? I assume the original coil is a 12V one? Out of interest what is the value of the ballast resistor?

In the old days I remember the ballast resistor being used to allow for a better spark whilst starting the engine. The ballast resistor would be shorted out whilst the starter was engaged.

Peter

[hutch6610]

Ballast resistors purpose is to reduce the voltage sightly in to the coil so it runs cooler. Your coil is most certainly receiving full 12v and i bet it runs hotter.
You are quite correct that the wiring diagram does not always match reality
Electronic ignition is supplied its own 12v & earth, it triggers the negative side of the coil, this also gives you the rev counter signal, think its a blue wire.

Connect the wires as follows:
Positive (+ Red) feed connects to the ballast resistor first and then connects to the coil via a short length of yellow wire. You should have only three wires to the coil. The short yellow to the +side of coil, Two wires go to the negative - side of the coil (trigger from ignition and rev counter)

Its possible the ballast has failed so its by passed? Also what are those two green wires?

[JohnFol]

I took an engine bay photo a while ago before taking bits off, so not the best image of the coil or wires going to or from. The green wires are actually just 1 wire from -ve to the electronic ignition (which I guess drives the rev counter??)

I had a look at the part number for the electronic ignition and found this diagram. So, I've followed the diagram (and it matches Lancia diag), but take your point someone might have shorted out the ballast if it was faulty. I will check

[mangocrazy]

When investigating why my electric Huco fuel pump was only working intermittently, I discovered that the coil (the input to which I was using as a 12v switched source) was actually only receiving slightly over 7v due to the ballast resistor doing what it was designed to - lower the voltage. If you've fitted a new, modern coil I would personally dispense with the ballast resistor. If it's NOS and of same spec as OE, then continue with the ballast resistor.

Once you've satisfied yourself with the wiring, of course.

[peteracs]

Hi Graham

I think you may need to be a little more careful.

I wonder if the ballast is there to limit the current through the electronic ignition, so if you put a coil with too low resistance then you may end up burning out the input circuit to the electronic ignition. It may of course be there for other reasons, but worth checking the coil impedance.

Peter

[JohnFol]

Hi Peter, bit worried about blowing the electronic ignition so I'm after a sanity check. With all wires disconnected

• old coil - 2.1 ohms
• new coil - 2.3 ohms
• ballast - ~2.4 ohms

O-level electronics suggests I will only get ~6v at coil so perhaps that explains why the previous owner shorted it out, i.e. 12v better than 6v at coil

I am looking at the carb set up next, but want to make sure the electrics are correct.

Graham, I too am taking a feed from the 12v side of the ballast to a huco, in my case it's via a relay. Would you mind (or anyone) measuring the ballast resistor whilst disconnected to see if it's similar to mine, or 0.9 ohm as the diagram I posted suggests it should be?

[peteracs]

Hi John

I am away for the next week or so, but will measure the coils I have, I should have electronic ignition and have standard ones to see what the values are. Not sure if I have the ballast resistor.

Peter

[JohnFol]

Spoke to Ignition Car Parts who tested their stock Bosch 0 227 900 002 and it was 1.5 ohm. I found a few on eBay with same bosch number and they seemed to be stamped 0.9 , so not sure where to go from here..

[mangocrazy]

Hi Graham

I think you may need to be a little more careful.

I wonder if the ballast is there to limit the current through the electronic ignition, so if you put a coil with too low resistance then you may end up burning out the input circuit to the electronic ignition. It may of course be there for other reasons, but worth checking the coil impedance.

Peter

I'm not about to do anything precipitate just yet, but when I fit the new engine a raft of other upgrades will go in, including an MSD ignition boost box and an uprated coil that can easily handle a full 12v. Electrics aren't my strong suit, but isn't the ballast resistor's function to reduce the voltage to the coil, not any other part of the circuit? Please correct me if I'm wrong (I frequently am, when it comes to vehicle electrics).

[JohnFol]

I think you are correct.

I should have asked the people who supplied the coil if its designed to run at 12v or 9v

[peteracs]

Hi Graham

In answer, yes the ballast resistor will limit the voltage on the coil in a direct ratio to the ballast and coil impedance. However the question is why have a ballast resistor if a coil rated at 12V nominal is available? That is why I wondered if the ballast was added to protect the electronic ignition (and use a lower voltage rated coil?). On the points system there is as you would expect no ballast resistor, just a 12V coil.

Peter

[mangocrazy]

Hi Graham

In answer, yes the ballast resistor will limit the voltage on the coil in a direct ratio to the ballast and coil impedance. However the question is why have a ballast resistor if a coil rated at 12V nominal is available? That is why I wondered if the ballast was added to protect the electronic ignition (and use a lower voltage rated coil?). On the points system there is as you would expect no ballast resistor, just a 12V coil.

Peter

Yes, that is the question... I can't think why Lancia didn't fit a genuine 12v coil either. I'm not even sure if my OE coil would tolerate a full 12v - frankly I doubt it. I do know that only about 7v is getting through to the coil as it stands with the ballast resistor in circuit. I think I might give H&H ignition a call (they refurbished my distributor a while back).

[mangocrazy]

I called H&H up immediately after posting above, and explained the setup. Their view was that the ballast resistor was there to reduce voltage to the coil and their advice was to remove the BR and fit a new 12v coil. Their view was that electronic ignition components are more sturdy than points systems, are designed for 12v operation and would be unaffected by any removal of the BR.

I'm tempted to remove the ballast resistor from the circuit and see what effect it has. I'll probably have a new 12v coil standing by in case the OE one releases its smoke. Looking back through an earlier thread, a guy I know from GC's forum expressed the view that standard coils 'don't like more than 9v', so if intending to dispense with the ballast resistor it would be prudent to ensure any new coil will be happy receiving a full 12v (and possibly a bit more).

[peteracs]

Hi Graham

More sturdy than points eh, no idea what that means, bit like comparing apples and pears to me.

Anyway, I do agree that running a nominal 12V coil (they must be designed to run 14V given the normal charging regime) with modern electronic ignitions would be the norm. However if you are looking to run the OE electronic ignition, remember it was designed mid 70s and the electronics then were very much on a learning curve so the ballast resistor may/should be considered part of the electronic ignition not just an ancillary component. It may not have been included in the ‘box’ simply because of its size or heat dissipation.

I am happy to be corrected, I just cannot see why they would add an extra component just for the hell of it and change the coil at the same time from the points version.

Peter

[mangocrazy]

I dimly remember that one of the advantages of electronic vs. points ignition was that the 'recovery time' between sparks on electronic ignition was appreciably greater than with points (something to do with dwell angle?). Perhaps Lancia added a ballast resistor in circuit to stop the coil overheating when used with electronic ignition rather than points? This is pure quesswork, by the way. I'm well out of my depth with vehicle electronics.

[JohnFol]

ok, for completeness of information I spoke to the Intermotor (SMP europe) and they dug out their old parts catalog.

• Bosch 0 221 122 031 is a direct cross to Intermotor 11330 (hence why I bought it)
• InterMotor show 11380 as the direct replacement
• Lancia 82303852 also maps to Intermotor 11040 (non-ballast coil for standard ignition)

The difference between the 2 lead candidates are

• Primary resistance of 11330 is 0.73 ohms / secondary resistance 6.8 kohms
• Primary resistance of 11380 is 1.59 ohms / secondary resistance 9.98 kohms

... and that's when my brain stops working

This is from Eric in a different thread
"My Lancia technical book gives the coil resistance figures as 1.2 to 1.6 Ohms Primary winding at 20 degrees c. secondary winding 6000 to 10000 Ohms. They are significantly different to a coil for points including the earlier points Marelli item. You can look at later dry coils if the resistance figures are close. The IE Dry type is primary 0.42 to 0.46 secondary 7560 to 9240 Marelli BAE 500B so not suitable."

I think I just need to get out and drive it to see if there are any issues and go from there