Poor Ignition Coil Reliability (thoughts?)

[Bill_qaz]

Not even going to take it off, just going to reroute the black wire the other side of the HT lead and make sure the terminal is secure. The coating on the top looks like underseal
Will know better when heater duct is moved to give better access. The duct isn't bolted to the inner wing as it was retro fitted.

On the cars that had the duct fitted at the factory, it is held on the inner wing with brackets. These are still available but generally poor quality and prone to rapid rusting. There's a Mini supplier (Nippy Cars) that sells nice black powder coated brackets that don't rust. My car has those brackets.

Stephen

Yes I bought a pair but with all the stuff on inner wing I'd have to move bits so just used 1 cable tied to bonnet pull to stop the pipe flopping.

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[svenedin]

Not even going to take it off, just going to reroute the black wire the other side of the HT lead and make sure the terminal is secure. The coating on the top looks like underseal
Will know better when heater duct is moved to give better access. The duct isn't bolted to the inner wing as it was retro fitted.

On the cars that had the duct fitted at the factory, it is held on the inner wing with brackets. These are still available but generally poor quality and prone to rapid rusting. There's a Mini supplier (Nippy Cars) that sells nice black powder coated brackets that don't rust. My car has those brackets.

Stephen

Yes I bought a pair but with all the stuff on inner wing I'd have to move bits so just used 1 cable tied to bonnet pull to stop the pipe flopping.
20250213_151437 (1).jpg

As you say, with all of the stuff on the wing the duct could not sit against it like it does on those cars that had it fitted at the factory.

Stephen

[svenedin]

Looking at the workshop manual AKD530 the coil specified for the 1098cc is Lucas LA12 with a primary resistance of between 3.2 and 3.4 Ohms.

All of the internally ballasted coils on sale these days seem to be 3 Ohm with the exception of the Bosch Blue 922081083 which is quoted as 3.4 Ohms. Whether this small difference in resistance has any bearing at all on failure rates I don't know but it seems unlikely. At 12 volts an increase in resistance of 0.4 Ohms decreases the current flowing through the coil from 4.0 amps to 3.53 amps as compared to a 3.0 Ohm coil.

The voltage required to jump a 0.025" spark plug gap is around 8,000 volts at the pressure in the cylinder and with the presence of fuel. The voltage required is a lot less in room air. "Sports" or high output coils claim very high output voltages e.g 40,000 volts but at the standard plug gap they reach nothing like that voltage. These high output coils have very many more secondary windings (because they are similar to a step-up transformer) and so I wonder whether they are a lot more fragile as a result. Only reliable failure data (which we do not have) would answer this.

Stephen

[michael4]

Not long ago I removed the 'Spitfire Multispark' from the coil to distributor lead.

Guess what...no discernible difference.

I am inclined to open it up and see what is in inside.

[svenedin]

Not long ago I removed the 'Spitfire Multispark' from the coil to distributor lead.

Guess what...no discernible difference.

I am inclined to open it up and see what is in inside.

According to this https://www.nortonownersclub.org/forum/ ... spark-unit it consists of two ferrite washers and a gap. Sounds like Snake Oil like so many ignition related products!

Stephenn

[Bill_qaz]

[/quote]

As you say, with all of the stuff on the wing the duct could not sit against it like it does on those cars that had it fitted at the factory.

Stephen
[/quote]
I believe when the fresh air intake type heater was introduced the DB10 unit for flasher was no longer used, so more space available on inner wing.
Your horn being on offside, is that the position for second horn when hi and low tone used? Or at some point was the single moved from nearside to offside? Mine is definitely OE wiring to nearside front position.

[svenedin]

As you say, with all of the stuff on the wing the duct could not sit against it like it does on those cars that had it fitted at the factory.

Stephen
[/quote]
I believe when the fresh air intake type heater was introduced the DB10 unit for flasher was no longer used, so more space available on inner wing.
Your horn being on offside, is that the position for second horn when hi and low tone used? Or at some point was the single moved from nearside to offside? Mine is definitely OE wiring to nearside front position.
[/quote]

I think for late cars like mine, offside (for RHD) is the normal position for a single horn. Certainly when I fitted the new wiring loom that was where the horn wires lined up. It could not be on the nearside without wiring modification. I must have a look and see if there are any mounting holes on the nearside. I don't think so.

Stephen

[MikeNash]

Svenedin asks for “thoughts or experiences”, so may I recommend a brand of coil? I think he should consider the Runbaken oil filled coil that was popular in the 1940s and 50s, and that’s shown and discussed on the Austin 7 site here https://austinsevenfriends.co.uk/forum/ ... p?tid=7364
Launched in 1941 it was some two to three times the cost of the current Lucas coil, and it came with a two year guarantee. (Which I suspect that was very unusual for the time.) It also had a cast alloy holder with a unique serial number, all of which suggests to me that it was a well-made product with careful quality control. There’re still many around on ebay, etc and that they’ve lasted is itself a recommendation. Finally, because the coil is contained in a glass bottle, Svenedin can eyeball the innards to assure himself it’s still all stuck together properly.
I’ve a 6 volt example with what looks like a period ballast resistor, a block of carbony material ¾ inch in diameter and ¼ inch thick. With 13 volts applied to the primary the coil gives an output of 32kV and with the ballast resistor in circuit it gives 21kV. I like period aftermarket bits and so I recommend to you all the Runbaken coil; fit one, it’ll brighten up your engine bay!
The only “downside” is that the oil may be PCB (polychlorinated biphenyl) which is dangerous, so if you break it (unlikely, it’s very tough) don’t touch the stuff or sniff or drink it. MikeN.

[svenedin]

Svenedin asks for “thoughts or experiences”, so may I recommend a brand of coil? I think he should consider the Runbaken oil filled coil that was popular in the 1940s and 50s, and that’s shown and discussed on the Austin 7 site here https://austinsevenfriends.co.uk/forum/ ... p?tid=7364
Launched in 1941 it was some two to three times the cost of the current Lucas coil, and it came with a two year guarantee. (Which I suspect that was very unusual for the time.) It also had a cast alloy holder with a unique serial number, all of which suggests to me that it was a well-made product with careful quality control. There’re still many around on ebay, etc and that they’ve lasted is itself a recommendation. Finally, because the coil is contained in a glass bottle, Svenedin can eyeball the innards to assure himself it’s still all stuck together properly.
I’ve a 6 volt example with what looks like a period ballast resistor, a block of carbony material ¾ inch in diameter and ¼ inch thick. With 13 volts applied to the primary the coil gives an output of 32kV and with the ballast resistor in circuit it gives 21kV. I like period aftermarket bits and so I recommend to you all the Runbaken coil; fit one, it’ll brighten up your engine bay!
The only “downside” is that the oil may be PCB (polychlorinated biphenyl) which is dangerous, so if you break it (unlikely, it’s very tough) don’t touch the stuff or sniff or drink it. MikeN.

Thank you Mike,

I do wonder whether it is the PCBs that made old oil filled coils nearly immortal !

It's amazing how long old electrical equipment lasts for. I have an electric doorbell that was made in the late 1890's. It has platinum contact breakers and it is still going strong. Beats that modern rubbish!

Stephen

[Bill_qaz]

Stephen
Old electrical test equipment for your old electrical devices

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[svenedin]

Stephen
Old electrical test equipment for your old electrical devices
20260812_213458.jpg

Yes that's exactly the kind of thing. Lovely wooden cases, brass bits. Marvellous!

It's stretching the topic a bit but this is my 1890's doorbell. The coils here still work perfectly (and the points which are platinum). No condenser here to stop the sparking. If these coils last over 125 years why do modern ignition coils fail in 5 minutes?

Stephen

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[myoldjalopy]

Very nice bell! Mine is just as old but entirely mechanical.
If these coils last over 125 years why do modern ignition coils fail in 5 minutes?
I guess:
1. Better made by real craftsmen than is modern stuff
2. Your bell has less work to do. Every time you take the car out, the coil is constantly working, the door bell gets less use
3. Coil in car produces a much higher voltage?
There may be other reasons........as I said, all this is guesswork.

[svenedin]

I was at a car show today (Capel, Surrey) and all the cars from my MMOC branch were parked next to each other. We all arrived at more or less the same time and all of us had driven far enough that the engines were well up to operating temperature. It was a warm day, 28 C, not as hot as it has been of late (35 C +).

Of the coils that were mounted on top of the dynamo, or in some cases on top of the alternator, all of them were too hot to touch except briefly. Two cars had the coil mounted on the inner wing in the same position that Bill has his coil mounted. Those coils were only mildly warm.

One branch member recalled how he went through a stint of the coil failing every few months until he fitted an old coil removed from a Minor that was being scrapped. That coil is still going a decade later (and it was already ancient).

Stephen

[Bill_qaz]

So my old real Lucas coil mounted on the wing is the best of both options

[svenedin]

So my old eal Lucas coil mounted on the wing is the best of both options

Definitely. I will give moving the coil to the inner wing serious thought. My car ran perfectly today with a Pertronix 3 Ohm resin filled coil on it. Martin Jay (Distributor Doctor) told me they have sold thousands of these, all over the world, and they just do not hear of failures with those coils. I would beg to differ as I had one fail within 5 minutes but that seems to have been very bad luck and it was replaced without quibble (it came from a VW supplier, not Distributor Doctor).

Stephen

[svenedin]

Very nice bell! Mine is just as old but entirely mechanical.
If these coils last over 125 years why do modern ignition coils fail in 5 minutes?
I guess:
1. Better made by real craftsmen than is modern stuff
2. Your bell has less work to do. Every time you take the car out, the coil is constantly working, the door bell gets less use
3. Coil in car produces a much higher voltage?
There may be other reasons........as I said, all this is guesswork.

Thank you. Well I am a bellringer so it has to be a nice bell!

Yes that's true. They both work on 12 volts but the duty cycles of the doorbell are nothing compared to the car ignition coil. The doorbell is only used for a few seconds so it doesn't have a chance to heat up much and it isn't in the heat of an engine bay either.

I have become quite fascinated by the subject. Apparently some of the modern coils that are mounted on the engine where there is a coil per cylinder are able to withstand 200 C. That would be way in excess of what a coil on a Minor would need to cope with. These are all epoxy resin potted coils. They are filled under vacuum so that there are no bubbles in the resin. Once the resin has set hard, the fine wires are protected from even severe vibration.

Stephen