26 replies to this topic

[Tornado99]

My '88 car came from previous owner with a Pertronix electronic ignition and Flame Thrower II coil fitted. Been working great first year of my ownership. Until yesterday when after a few hours of driving around town, engine suddenly quit and would not re-start,,,,cranking fine, fuel & pump good. Checking things today, I note infinite Ohms (open circuit)  between the coil primary terminals, so I assume that means it has died?

 

This coil is labelled 0.6 Ohm and I run it off a direct 12 v feed from fuse #1....as I removed/by-passed, some months ago,  the pink/white ballasted connection, based on what I've read on several threads on this forum. Was that a mistake and has this lead to frying the coil? 

 

From the FlameThrower II instruction guide, I see this table:

 

 Capture.JPG   64.9K   3 downloads

 

If I understand this correctly, the 0.6 Ohm coil is not for 4 cylinder cars and from the text below the bolded ballast warning, it implies to leave ballast if primary resistance is lower than specified. So I should have left it running off the ballast wire?

 

 

Which of the listed ones should I try to get?

 

Thanks.

Edited by Tornado99, 23 May 2021 - 10:20 PM.

[nicklouse]

Have you removed the ballast? Or not? Pick the correct coil for your application.

 

it has little relationship to the dizzy. 

[Tornado99]

Yes I removed the pink/white connection to the +ve coil terminal and ran a new line from the #1 fuse terminal (switched 12v on with ignition) direct to the +ve coil terminal. Was running that way for several months. 

Edited by Tornado99, 23 May 2021 - 10:57 PM.

[croc7]

I am converting my mini from points to electronic ignition using the Pertronix II module. The included instructions were vague regarding which coil to use; the chart stated to use a coil with a resistance between 0.6 - 3.5 ohms but that the coil must meet the “MINIMUM primary resistance REQUIRED in the resistance chart”. Huh??

So I called Tech assistance at Pertronix and asked if I could use my 3.0 ohm Bosch coil, which met the parameters of their chart? The reply was, ‘no, the Pertronix II module requires a 0.6 ohm coil. Maybe a 1.5 but 0.6 is ideal, a 3.0 ohm coil will overheat and leave you on the side of the road until it cools down.’

After this rambling, what I’m saying is that years ago, I installed a Pertronix ignition on the MG1100 (pre-Pertronix II) using a 3 ohm coil and it starts and runs great.

For what its worth, if your module is not Pertronix II, perhaps you should be using a 3 ohm coil rather than the 0.6.

Hope that helps.

[Tornado99]

I am converting my mini from points to electronic ignition using the Pertronix II module. The included instructions were vague regarding which coil to use; the chart stated to use a coil with a resistance between 0.6 - 3.5 ohms but that the coil must meet the “MINIMUM primary resistance REQUIRED in the resistance chart”. Huh??

So I called Tech assistance at Pertronix and asked if I could use my 3.0 ohm Bosch coil, which met the parameters of their chart? The reply was, ‘no, the Pertronix II module requires a 0.6 ohm coil. Maybe a 1.5 but 0.6 is ideal, a 3.0 ohm coil will overheat and leave you on the side of the road until it cools down.’

After this rambling, what I’m saying is that years ago, I installed a Pertronix ignition on the MG1100 (pre-Pertronix II) using a 3 ohm coil and it starts and runs great.

For what its worth, if your module is not Pertronix II, perhaps you should be using a 3 ohm coil rather than the 0.6.

Hope that helps.

I agree that the instructions on their site are vague (see the screen capture chart I posted). What I think we need to know, is do we run the ballast resistor wire to power the coil if it is 0.6v? The ballast wire supplies something like 8-10v during normal operation, and the added line from the starter solenoid boosts that to 12v for start up only. From the chart, 0.6 Ohm coil is only listed at two places, both for 8 cylinder engines and only for 6v supply. 3 Ohm is shown for 12 v on 4 & 6 Cylinder. 

[nicklouse]

That chart is simple.

 

no ballast (as it says) and your coil is the 3Ohm one. You should not be using the 0.6 

[Ethel]

I'd say the same, the coil will likely be designed to survive being in a closed circuit at the stated voltage. It's more likely to be an issue for the electronics down stream of it.

 

If you kept the ballast wire and also ran the ignition module off it then it would be nearer to 6 volts. But not reliably so when the bypass is connected by the starter. It'd be simpler & safer to remove the ballast & just run it as a 12v system.

[nicklouse]

But the 6v is for older cars that ran the whole car on 6v like early cars. 

[Ethel]

Motorbikes are likely the main target market. Using the coil & ballast as a voltage divider would give you 6V, but we can agree that'd be  "pointless" 

[Tornado99]

Found this on the Aussie Pertronix site :

Now the maximum system amperage can be determined. Divide your voltage measurement by your coil resistance measurement. This will give you the system current or amperage.

" Four and six cylinder engines should not exceed 4 amps. Eight cylinder engines should not exceed 8 amps. If the total amperage in your system is higher than the amount recommended for your application, you should install a ballast resistor.

Example:
Voltage 12
Resistance 1.5
12 / 1.5 = 8
Total amperage is 8. "

So with 12v feeding primary terminals, 0.6 Ohm coil gives 20 Amps of current through the primary windings. This is likely why it eventually failed.

http://www.pertronix...e run position.

[Tornado99]

ACK!

Now I see this specifically on the Flame Thrower 2 coil:

 

 Capture.JPG   80.27K   1 downloads

 

Note it says FT 2 0.6 Ohm is good for 4 Cylinders with 12v supply when running Ignitor 2 (which I am). Also, FT 2 is only made at 0.6 Ohm.

 

So if this is correct I don't know why mine failed....

Edited by Tornado99, 24 May 2021 - 06:36 PM.

[Tornado99]

OK, I think I'm getting it now....just watched this nicely explained 4 part video on ballasted coil systems:

 

 

Upshot is the ballast lines in our older cars was put there to permit decent coil performance when battery voltage drops due to cold temps and starter motor cranking. The ballast by-pass line feeds max battery volts to the coil while cranking for startup, then goes off with starter shut off...that's when the ballast line feed takes over at less than full battery volts to the coil. This prevents the coil running at excess Amps, leading to over heating of the coil and damage to the breaker points and even electronic ignition systems. 

At 12v feed to a 0.6 Ohm coil, that's 20 Amps...which is 240 Watts of power inside the coil....that's extremely high! And recall, once battery is topped up, the alternator keeps a charge voltage at 13-14,2 volts....that is what an unballasted coil would be getting, so even worse for the coil heat build up. 

 

A 3.0 Ohm coil can run fine unballasted at 12v (producing about 50 Watts). But it will struggle as temps dip/battery output drops to 8 or 9v while cranking etc. A 1.5 Ohm coil plus a 1.5 Ohm ballasted supply line will give you same power as unballasted 3 Ohm coil....but with the 12v bypass while starting, it will allow good starting when battery is lower. 

Edited by Tornado99, 24 May 2021 - 07:53 PM.

[croc7]

Found this on the Aussie Pertronix site :

Now the maximum system amperage can be determined. Divide your voltage measurement by your coil resistance measurement. This will give you the system current or amperage.

" Four and six cylinder engines should not exceed 4 amps. Eight cylinder engines should not exceed 8 amps. If the total amperage in your system is higher than the amount recommended for your application, you should install a ballast resistor.

Example:
Voltage 12
Resistance 1.5
12 / 1.5 = 8
Total amperage is 8. "

So with 12v feeding primary terminals, 0.6 Ohm coil gives 20 Amps of current through the primary windings. This is likely why it eventually failed.



http://www.pertronix...e run position.

I’m using both Pertronix II products, the 0.6 ohm coil and the Ignitor II module because they were designed to be used together and should work, reliably. (Nonetheless, I’ll carry a spare 3 ohm coil and points/condenser in the boot. Belt and braces, ya know!)

I’m curious, what ignitor module was installed in your distributor with your 0.6 ohm coil?

Edited by croc7, 25 May 2021 - 11:14 AM.

[Tornado99]

I have the ignitor II in the distributor (59D4). So both were Pertronix II components.

Regardless of what the guide chart says, it appears running such low resistance coil without a ballast to reduce input voltage is not good long term.

Strangely, my car has a pink/white line to the coil, which should be the ballast supply. but it measures in at 12.5 volts, exactly what my new line direct from fuse 1 measures. Seems it is not ballasted. Wiring harness may have been modifed by previous owner to remove the ballast resistance or maybe some kind of failure in the ballast line. My 0.6 Ohm coil was getting full battery/Alternator output since before the past year i've owned it. Failed two days ago. Ive confirmed other components, ignitor etc still work to operate a different coil I tested. So only FT II is bad (reading open circuit on + to - terminals).
I will fit a 3 Ohm replacement, and that cannot be a FT II.

[sonscar]

The ballast wire may well measure 12v with a Meter but will be less when under load.Calculating the coil current is tricky because it is not turned on all the time.What is the dwell time with this igniter?not as simple as it seems.Steve..