Hi,

I've seen a few posts lately on the subject of Ballast Resistors and Ignition Coils so I've put together a few words on the subject which I hope will throw a bit of light on the subject for those less familiar with Electrical stuff (although I'll probably confuse the daylights out of everyone). I haven't gone onto detail as there are a lot of variables and I've kept away from formulas as they reminded me of warm June days sweating over my Electrical Engineering Degree exams when I should have been at the Isle of Man watching the TT. I've also focussed on the 6 Volt systems as those are the ones I have had practical experience on (Fords and my MGB)
Richard

Hi Richard

An excellent post and attachment Somewhat coincidentally, mid week I sent off for a PowerSpark electronic CB replacement device and today thought I'd fit it, thinking it would be a 30min job, tops.

It was indeed quick to fit but there was no sparks after i fitted it My car was already fitted with a Panda 30 coil and thus runs without the rotor arm/dizzy cap as a wasted spark system. It didn't cross my my this would matter. Anyway, I called Powerspark and they asked what the primary coil resistance was as it must be 3-4 ohms for their electronics to works. And of course it wasn't, it's 1.7 ohms:bang: I described the look of the coil and they said 'ah, that's an electronic coil', it won't work, you need an older style coil with 3 ohms.

It was 3pm and they close then, so I left it and had a cuppa and a ponder. I'd rather keep the twin output coil/waster spark system as I like the simplicity and reliability of loosing the rotor and cap.

So I had a bit of inspiration. No doubt utterly obvious to you and many on the forum, but I though, why not keep the set up but use a ballast resistor to bring up the resistance? A quick look on Google revealed they are generally 1.6 ohm, so I should get 3.3 ohm in total (see that Maths, eh?!).

So I got one at the local motor factors down the road for only a fiver. Tomorrow morning, unless someone tells me, "it's not going to work because ....." The guys at Powerspark didn't suggest it so maybe it's not going to be that easy. But as mentioned unless I hear 'Noooo' from anybody I'll wire it in series on the pos side and see how it goes.

Viggers

Not sure I understand why you think you need 3.3 ohms instead of the recommended 1.6 ohms ballast resistor. 1.7 ohm coil resistance + 1.6 ohms = 3.3 ohms resistance, which is what the Powerspark folks told you what was needed. Maybe I missed something?
John

Hi John

You have got it right, not sure where the confusion is but obviously I'm not explaining myself properly. My current Panda coil on it's own is 1.7, the ballast resistor I just bought is 1.6, so I have a total 3.3 ohms which is where Powerspark said I need to be.

Tried it out today, confirmed with my mulitmeter that the Powerspark is now indeed seeing a 3.3ohm load, but still no joy. No spark being generated. So had to go back to my good old points for the time being.

Any ideas?

Viggers

This is basically identical to the Pertronix system (USA). I see on the Powerspark web site they note: "Please ensure that your Live ignition feed is on the +'ve side of the coil ready for your Powerspark Red wire and no power is on the -'ve side ready for the Powerspark Black wire."

You might double check this.
John

Hi Viggers,

I'm not up on Panda30 coils but I assume that if the primary resistance is 1.7 ohms and it's not a ballasted system then this coil is designed to work with electronic ignition (maybe the Panda owners out there could verify this).
At 1.7 ohms this coil will draw 7 amps which is not suitable for a contact breaker system as the points will be short lived. It is designed for a high powered solid state switch.
Although the Powerspark Module is designed to work with 3 ohm coils, sticking additional resistance in the coil's wiring will probably not help as you have effectively dropped the voltage across the coil by half and hence halved it's power output.
Also did you take the module feed (red wire) off a 12V supply. If you have connected to the coil then it will not be getting the correct supply voltage.
Richard

Personally i never used it, in some cars i have a dry coil & others a double coil. Put the ignition on and start the car right away. I have never had any problems. If you leave the ignition on of course it will heat up.

Hi Richard

You assume correct and it's not ballasted as standard, so the draw is high and the points suffer. There is an Italian eBay seller with Panda 30 coils for use on 500's and he says, "IN THE CASE THAT THEY SHOULD BE FITTED WITH ELECTRONIC IGNITION,RECOMMEND THE USE OF A RESISTANCE DA 1,5 OHM TO BE MOUNTED IN SERIES ON THE POSITIVE LEAD FROM THE IGNITION SWITCH. THIS RESISTANCE HAS THE PURPOSE OF LOWER THE INPUT VOLTAGE TO AVOID OVERHEATING, INCREASING AND IMPROVING QUALITY 'SPARKLE."

I put the additional resistance in series on the Powerspark module, so it will dropping the voltage to the coil.

I wired the module as per the instructions, so red module feed wire connects to the coil 12V supply. But it's is parallel so both the coil and module get full voltage.

I've emailed the guys at Powerspark, lets see what they say. Maybe the only solution, if it exists, is to find a module that is happy switching 1.7 ohms.

Viggers

I've been restoring cars for 26 yrs, in some customers i have seen it mounted on, in all my personal cars i have had & sold i have changed the entire wiring loom to avoid problems in the long run. I have also put in a new dry coil & i repeat again i have never had any problems at all. Some people may still have an original wiring loom of 50 yrs old plus & think that with one resistance it will preform miracles. Along with a dry coil of 20 yrs plus. [emoji1360]

New problems have arisen with my engine. They are a bit off topic but relate to my last post.
Powerspark got back to me and kindly send out a new unit, before I even asked them for a replacement. So good news there. I just fitted it, with the ballast resistor, and I get a strong spark and she (eventually) fires up.

New issue#1: The oil light won't go out even after a 1 minute of running.
I dare not run a car that long normally with the light on, but trusted that nothing was wrong in the engine a couple of weeks ago so ran it for a minute. It was -5 degrees last night and I'm running a classic 20/50 mineral oil. Could this be the issue, oil too think? But I'd have thought that would cause high pressure? Engine sounded normal BTW. Not anything to do with diodes in the Powerspark? I know that sounds like a weird thing to suggest as it's a different circuit but when I was changing my dash oil warning light to an LED it also wouldn't go out, so changed to a normal bulb and it was back to normal.

New issue #2 :
Possibly related but hope not. When attempting to start the engine it cranks at normal speed for say 5 secs then almost comes to a stop, then continues as normal, as if the compression has changed momentarily. I charged the batt last night on one of those intelligent chargers in preparation and this morning, and even had it jumped to my sons Polo for more oopmh and it still did this behavior. I've put it on on old fashioned 6amp charger now to see what happens.

All help gratefully received.

You should stop running the engine until you can diagnose the oil pressure issue. I would go buy a cheap mechanical oil pressure gauge and install it in place of the current sending unit. When the engine starts you should see an immediate 40 psi (2.7 bar) pressure. If it is low you have an engine problem and should immediately switch the engine off.
If pressure is good cold, then when the engine is warmed up, at idle, you should see 10+psi (0.7 bar) of pressure. If lower than this then you have an engine problem.
For the current problem with turning the engine over, I would make sure the cam and crankshaft timing is correct, and that the valve clearances are set correctly, and that the Powerspark ignition system is timed correctly.
Not to alarm you, but worse case is the engine is binding due to lack of oil lubrication.
John

Thanks John. Good advice.

What I don't get is this: Engine was running perfectly when I last took her out for a drive for several hours three weeks ago. Two weeks ago I (attempted to) switch over the contact points to electronic ignition but I had a faulty unit. Left things for two weeks due to lack of time. Today fitted the new electronic ignition unit and I find I have the oil pressure and cranking problems.

What gives?!

I don't think the oil pressure problem is related to the new ignition system. The only way the new ignition system could cause the cranking issue is if it is firing the plug at the wrong time.
Disconnect the center coil lead from the distributor and try cranking the engine for a short time and see if there is a difference.
John