I did sound nasty in my defense of Scott, and didn't mean to be. The "scary" comment had to do with possibility of damage to the Pertronix. Any ignition coil, (transformer that it is) works by storage of energy in the field, and then kickback from the collapse of the field when disconnected from the power source. That's where the spark comes from as the secondary field collapses. But the primary has kickback too, and that voltage spike comes right out and hits the ballast. The scary part is hooking a solid state device to such a transient laden power source.
On the issue of 12v or 24v, I'd suggest the box your Pertronix came in might have been a 12v unit. Thus the understandable confusion. Way back when, in the '90's, when we were first seeing 404's come into the country, someone (John Wessels? or others in parallel efforts?) approached Pertronix to design a unit for our trucks in 24v. I really don't think Scott would have said the units need 12v. He's been around these special 24v Pertronix from the beginning.
As for the Pertronix box specifying connecting to the coil for power, coils have a "batt" terminal tied to vehicle power. That establishes the 'high' end for the coil's primary, and the Pertronix, or points, grounds the 'low' end then ungrounds it when a spark is needed. BTW, the period of time the points held the primary charging is the Dwell time, measured in portions of 360 degrees.
That coil 'batt' voltage suffers some spiky variation too, so why take a chance?
This +24V +12V conflict regarding the Pertronix ignitor is something I'd like to understand... The instructions clearly say to connect the red lead to +24V and, if using a ballast resistor, to connect it before the resistor.... Hammogger's explanation of voltage fluctuations between the coil and resistor fits with my understanding of how things work.
Me too. My kit slipped straight in and I had no trouble setting the timing without major movement of the distributor. Used Scotts instructions for connecting and it runs fine. The only downside is that it is noticeably slower to start than it was when the points were fitted. One possible reason is low voltage to the ignitor, which is connected at the input to the radio suppressor. Despite a range of equipment I've never been able to successfully measure the voltage at various parts of the ignition system.
Like most I have accepted Scotts recommendations, but as I am a curious B@#&* I'm always interested in why is it so.
The discussion here is great. Here is where we differ in our opinion from Pertronix. The ignitor is designed to run on a voltage range. Minimum 12.8-13.4 volts, and maximum 28 volts. If you do not have the minimum voltage the unit will not spark. If you overvoltage the unit it could fry.
It is quite common for a 404 spinning high RPM's to be close to 28V if not a little higher. Having a 1 Volt cushion does not make us very comfortable. However, when running the unit at post ballast resistor voltages 17/18 - 21/22 volts we still have a pretty good cushion both on the undervoltage side and the overvoltage side. We have been installing and reccomending this method in our literature for 8-9 years. (As a side, pertronix tech support reviewed our instructions years ago and did not have a problem with them.)
It's worth another look. I will talk with product development at Pertronix and see what they have to say. I believe we are in the 3rd generation of the module and some things have changed. For example, pertronix use to warn against splicing the Pertronix wires, that warning has been dropped and replaced with (use quality splices...)
Two Tone, I would suggest you replace your coil and I'll bet that will solve the missing problem. Then you can deal with your overvoltage issue if it exists. Extended periods of overvoltage are one of the most common reasons for the 40611 coil to fail.
It's worth another look. I will talk with product development at Pertronix and see what they have to say.
Hi Scott,
Sounds good. Can see the issue with a max 28v input as I'm on 28.8v at mid RPM. I can also see the rationale in Bobs comments about a clean steady input voltage so would an acceptable solution be to put in a quality voltage drop resistor to drop the input voltage by ~4v to provide a safety margin if it is still required.
You'll hate this but just done some numbers on my system (as I can't actually measure the voltages despite....) and I get 13.2v (calculated) at the input to the radio suppressor with the full pertronix kit. My actual resistances are Ballast 4.6, Suppressor .9, Pertronix coil 3, input voltage 28.8, cumulative ign cct resistance 8.5 Ohm, calc Ign load 3.39 Amp.
Using exactly the same process with my Mil components ie 6 Ohm for the coil gives a calculated 17.3v at the input to the suppressor, which is the voltage commonly referred to. Any chance that this is actually (physically) correct using the full kit????
Whilst you are on-line, did you manage to sort out the tyre inflation kit?
Two Tone, I would suggest you replace your coil and I'll bet that will solve the missing problem. Then you can deal with your overvoltage issue if it exists. Extended periods of overvoltage are one of the most common reasons for the 40611 coil to fail.
I've got no problem with replacing the coil but doesn't it make sense to first determine what caused it to fail?
When I installed the kit I had 18.9 volts at the ballast output, I now have over 25 using the same meter. This suggests to me that the ballast has 'changed' and may be faulty.
Should I not compare it to 63TLF8's resistance measurement of 4.9 ohms?
I assume that since the coil is a 3 ohm coil it should have a resistanc of 3 ohms across the primary winding. Can anybody tell me what the resistance across the secondary winding should be?
Shouldn't I be able to determine if the coil is faulty with an ohm meter?
If anybody knows please let me know, meanwhile I'll measure some resistances.
Thanks everbody.
__________________
Two Tone
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Reading the instructions - a sure sign of weakness and uncertainty.
I found some specs for the 40611 that state primary resistance should be 3.0 ohms and secondary resistance should be 8.5k ohms. Those are the exact values I get when I test the coil.
I checked the original Bosch coil: Primary 6.0 ohms, Secondary 11.5k ohms.
I replaced the Flamethrower with the Bosch and the truck runs perfectly again so it would seem that although the Flamethower is up to the resistance specs there's still something wrong with it.
The post ballast voltage is still 25+ so I'm guessing my ballast went bad and the over voltage ruined the Flamethrower coil. I got a resistance of 4.5 ohms across the ballast which is .4 lower than 63TLF8's measurement of 4.9 on his ballast. Not sure if that is a significant difference or not.
Scott, I'll be placing an order for another coil and a new ballast resistor right away. Thanks for the time and help.
If anybody has more input feel free.
I'll update when I install the new coil and ballast.
I got a resistance of 4.5 ohms across the ballast which is .4 lower than 63TLF8's measurement of 4.9 on his ballast. .
Two Tone,
My Ballast resistance is / was 4.6 Ohm. You may have seen the .9 Ohm suppressor resistance following that and rounded up. If you are showing 4.5 ohm, allowing for instrument calibration etc, I would say its OK.
By changing your coil you are also changing the voltages where you measure them in the system so there is always the possibility that may be connected to your problem. Also, correct resistance cold for your flamethrower coil may not mean that it's OK hot.
!)
but just done some numbers on my system (as I can't actually measure the voltages despite....) and I get 13.2v (calculated) at the input to the radio suppressor with the full pertronix kit. My actual resistances are Ballast 4.6, Suppressor .9, Pertronix coil 3, input voltage 28.8, cumulative ign cct resistance 8.5 Ohm, calc Ign load 3.39 Amp.
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