Well, apparently not me. Most of you know, if you've ever seen me try to nonchalantly and stylishly leave an establishment/cruise/petrol station/Pilates studio, that if my car doesn't start the first time, it will take anywhere between 10 - 20 goes before it finally fires up. On other occassions, my car would crank over fine but not fire and I'd end up flattening the battery. So today, I finally (think) I fixed it. Had planned to drop in to 34pissup's place and see if he'd finished that coupe yet. Jumped in my car and it did the cranking but no fire thing. I kept cranking it until the batter sounded like it was dead. So I hopped out with plans to plug in the batter charger and thought I would chuck a Voltmeter across the battery to see how 'dead' it was. 12.7 Volts. Hmmm... doesn't sound too dead to me. I've had a suspicion for a while now that I'm not getting enough voltage somewhere in the ignition system, so I thought I would check the voltage at the positive side of the coil (that's the side with the + on it, J ) 6.2 Volts. Hmmm... that doesn't sound right either. About this time flames rang to find out where my house was as he and Dr SP were cruising around in Miss Stickshift. They pulled up, we had a cup of coffee, talked shit, and they left. In case you're wondering, no, that doesn't have anything to do with the story. Now, getting to the point of the story, I fitted a ballast resistor to my ignition because I have a Mallory Magnetic Breakerless Ignition distributor (i.e. points-less, not point-less ) The instructions say you HAVE to have a ballast resistor otherwise you can burn the ignition module out (and they're EXPENSIVE). I know because I had to replace one once. So I checked the resistance of the ballast resistor. Printed on it is 1.2 Ohms, but putting the Multimeter across showed a resistance of 1.8 Ohm. I know from my very limited knowledge of electrical engineering that a higher resistance means a higher voltage drop. I also know that having two reistances in series - the other resistance being the coil itself - creates a voltage divider, i.e. the ~12 V of the battery gets split between the two resistances and as the coil also has an internal resistance of around 1.8 Ohms, the voltage was pretty much halved to just over 6 Volts. As a bit of a test, I bypassed the ballast resistor (and remember I had already 'killed' the battery) and after a couple of slow cranks, it fired up. What I wasn't sure about was whether this would damage the ignition module or not, so I did what all good auto electricians do and got on Google. It turns out Mallory have a pretty good website http://www.malloryperformance.com and they even have a Knowledgebase, so I typed in 'ballast resistor' and this is what I found. Mallory Knowledgebase Question: Does the unilite need to have the voltage stepped down to six volts like an automotive Ignition or can you use direct battery voltage thanks Solution: It's not really so much a matter of voltage as it is primary resistance. You need at least 1.4 to 2.0 ohms of primary resistance. This can be in the coil, in a ballast resistor, in a resistor wire, or in any combination of these. Most automotive coils have less than 1.4 ohms of primary resistance (measured between the positive and negative terminals of the coil) so a ballast resistor or resistor wire must be added. So, to cut a long story short, I bypassed the ballast resistor. Went for a drive, got the car warm, stopped a couple of times, got up it a couple of times and IT'S ALL GOOD! Extra revs and it starts no problem. Now I need to get a bit more mechanical advance in the dizzy to get the engine back to where it should be, but that's another story...
Very interesting post. I tend to go with installing the ballast resistors. You are correct that the ballast resistor and coil do form a voltage divider. The thing that the ballast resistor does that isn't realized is that it also limits current through the module. Without the current limiting, the module will get the brut force of almost driving a dead short. I would do something a little different. Find a way of bypassing the ballast resistor only when starting the engine. Should be able to do that with a small relay. If you want to PM me with a diagram of the circuit, I can provide a circuit for you.
If it's wired correctly, when starting, the ballsat resistor is bypassed and you get full batt voltage to the coil. Figure that out and go back to having the resistor in the circuit when running.
Thanks for the advice. I had it wired as per Figure 4 in the Mallory Wiring Diagram, which by my understanding shows that there's no way to get the full 12V to the coil. Can you show me how it could be done with a relay. I've got a spare one laying around, so I could probably manage it. Really don't want to burn out the ignition module.
You can connect a 12 ga. wire from the starter motor passive side of the switch to the coil and keep the ballast resistor. This way the coil gets full voltage only when starting. Some starter switches have a connection terminal for this very purpose. On the ones without you can add your own insulated terminal post.
As far as I know, all stock 12v ignition systems from the mid 50s to the mid 70s had a ballast resistor of some sort, and a bypass system also. Some had two different ignition switch terminals, some used the starter relay or solenoid to do it (look for an R terminal on the relay or solenoid, this would be connected to the + side of the coil). But when they started using high energy ignitions in the 70s, they started to do away with the bypass stuff on the switches and relays. If you give us the specifics of what parts are in your car, we can maybe help you figure out how to wire up the bypass circuit.
OK. Specific parts. Car is a '67 Rambler American. It's an AMC 290 V8. Distributor is Mallory MBI and I've also fitted one of those module protector box things (forget what their official name is). It mounts between the distributor and the rest of the electrical system and is meant to protect the module from wayward electrical spikes. Just had a look on their website, it's a 'Circuit Guard' Bosch GT40R coil. Starter motor is a Ford 'rat trap' type with an external solenoid. And of course, the aforementioned 1.2 Ohm ballast resistor that is actually 1.8 Ohm. Would an option be to put a lower resistance BR in the system?
For Ford starter relays, find one with 2 small terminals. One will be stamped with 'S' (that's the hot wire from the key or button to engage the starter). The other will be stamped 'I' - that will provide 12V to the + side of your coil. That's the easiest way to get it there if you have a Ford-style starter relay...as Squirrel says, they did away with that as they went to the Dura-Spark. So some starter relays don't have both terminals any longer... EDIT: Given your parts combo, find another starter relay with the two terminals. Run that wire to the coil. Here's a pic
Sweet. I've got a solenoid that looks like that, so I should be able to do it. I'm still not convinced that having only ~6V at the coil is a good thing, but I can't seem to find any literature that tells me what the max voltage should be without stuffing the module. I think I may need to get the 12V to the coil for starting AND change the BR to something with a lower resistance and try to get 9V or so at the coil, just to be safe.
All coils are 6 volt. (edit; should have said 'oem or original) That's the purpose of the ballast resistor after '56. That's why on a 6 volt system if battery isn't up motors are hard to start. In the days before 12 volt systems EVERYBODY that understood the difference bought 9 volt batteries for their cars because...........you got it. With 6-9 Volt to the primary, the secondary steps up the output(on discharge of the spark) to over 20,000 volts. No need for anything different. It's a function of ohms law. If a coil were designed to work with 12 volt, the wires in the primary would have to be smaller. They are already itsy-bitsyy-teensy-weensy! Open up your mind. Convince yourself, that a ballast resistor is necessary for proper function and NO, another one with less resistence won'nt change the spark voltage to a measurable. Like what do you want 18,000 volts as opposed to 18,000.5 volts? Putting 12 volt to the coil on start is a good thing. Putting constant 12 volt to the coil is a bad thing. You youngsters think it's necessary for change, just for the sake of change. Sometimes the best way is the original way, like round wheels!
There is a range of acceptable voltages depending on the coil...4-8 should function. The more voltage, the hotter the coil runs and the greater the risk of damage.
You nailed it. That's another issue, running 12 volt to the coil (in addition to taxing the electronic parts or points/condenser), it overheats the coil. (edit, after we know if it doesn't need an additional one.}
I did the same thing a few years ago, "bad advice from a couple buddies" anyway I made it 15 miles untill my almost new $60 Mallory coil over heated and burned up. Duke
I'd check with Bosch. I would not be surprised if the R in the coil pt. no. stands for resistor...as in a built in resistor. You could be doubling up on the resistor. Some coils have a built in resistor and don't use an external ballast resistor that we are used to. Just a thought. I'd check with them.
I mentioned this on another thread. Had a 67 F'bird, with a cracked resistor wire. Took a while to track it down. Put in a ballast resister with a cut out switch. When the switch was open I had a full 12V to start the car, shut the switch and it ran on 8V. It was a mini switch which doubled as a theft deterrent.
Im reminded, by myself, that all of this exchange hasn't fixed your original problem yet. Good discussion, but to what end?!!! If it were me, I'd try it awhile without the resistor. If that failed I'd try it with another coil, it could be your coil. Aside from that don't forget that it might not be the resistor or coil at all, it could be in the electronics................or something else entirely....................
I agree with the Mallory tech, that you only need 1.4 to 2.0 ohms resistance, which is already part of your coil, as you described and measured. No additional ballast resistor is required according to Mallory. My Pertronix ignition also only requires a coil with 1.5 ohm resistance. I have run this ignition on both my daily rides for many years without ballast resistor and no problems. Btw: An ignition coil is basically a transformer with a primary and secondary winding. A transformer doesn't care what voltage goes in, as long as the current rating is not exceeded. It's the ratio between primary and secondary that matters and the input and output impedance. Ignition coils create a spark at the plug to ground through the collapsing field across the secondary winding, when it is disconnected at the breaker points or electronic ignition. The dwell when points are closed determines how large the field gets. Higher ratio coils can build a larger field and can deliver a hotter spark. Also keep in mind, that lower or average quality ohm meters are not very accurate measuring 1-2 ohms. Find a metal resistor at 1 ohm with 1% or 2% tolerance to find out how accurate your meter actually is.
Well, it cares to some extent what the voltage is because the input voltage x ratio = output voltage. Now, would a one or two volt difference in the input change the output significantly enough to run poorly? Probably not in most applications. For the "typical" 40,000V hi-po coil, you've got a ratio on the order of 6600:1. 6V in ~ 40KV out. Each volt will equal about 6.6KV output change. This is grossly simplified and assumes full saturation....there are, as you're no doubt aware, many more factors.
Not to beat a dead horse, but the tried and true........ When cranking, is the spark bright blue and will jump over 1/4 inch? If so, your hard starting problem ain't your coil or resistor. Be set up so that when you have the problem again check the spark and see. That might narrow down your options.
Another important thing is to use the correct spark plug wires and spark plug type. Electronic ignition modules require 'suppression wires' and resistor spark plugs, which suppress RFI and EMI that could interfere with the proper function of the module. These wires need to be replaced periodically as the conductive coating wears out with use over time. More info here: http://www.magnecor.com/magnecor1/truth.htm
Tried last night, but the Bosch Australia website was down for some reason. Will try again today. The GT40R is a 40,000V coil, and I thought the 'R' meant you had to run a resistor with it, but it could be the other way around. It seems everyone you ask has a different answer! As they say though, the proof is in the pudding. The car starts easier and runs a lot better. There is no doubt the voltage at the coil IS making a difference.
Flat Ernie has the solution to your situation. Looking at the Mallory diagram, the module just takes the place of the coil, so just wire the I terminal of the Ford relay to the module side of the ballast resistor and you should be ok. The coils are meant for 6 volts.
Another point worth mentioning when checking battery voltage. When you put a volt meter to a battery it will read voltage around 12v even if dead. You have to put a load on it to see if its worth anything.
Yes R for resistor, a lot of cars get full voltage off the solenoid on the starter and have a spade terminal there for it.
I'm still a bit concerned though about the spark strength when running. I can see putting 12V via the starter solenoid will help with starting, but it will still mean there's stuff all at the coil. I understand how the coil multiplies the input voltage, but I know from the seat of my pants (and the extra revs) that it's running shitloads better with the higher voltage at the coil. As it says on the Mallory knowledgebase, if you've got at least 1.4 Ohm primary resistance at the coil, then you shouldn't need to run a ballast resistor. From other stuff I've been reading, it seems most stock coils are between 0.5-1.0 Ohm.
The Jalopy Journal
