Technical New guy with odd electrical problem

Maybe an odd question.

could bad plugs or wires cause an issue with the coil?

 

I heard they can, but they were all new 350 miles ago and have since been replaced in this process

 

Ok, I have a question. If I have a connection or wire with high resistance on the positive side but voltage is still good to the component and grounds are fine, would that cause the component to work to hard? Or just cause the connection or wire where the resistance is to get hot? Example: if the fan draws 25 amps under normal operating conditions with 14v input, but the connection from the relay to the factory fan positive wire has a lot of resistance and high ohms but voltage is still 14v, but the grind side is zero ohm, would that cause the fan to run hot and draw more amps, or just cause the connection to get hit and melt? My thinking is the fan would operate normally, but the problem would be before at the connection until the wire melted. Is this thinking correct? Just to be clear, I don't have a problem with the fan or wire, it's just an example. I'm just trying to think of other things to look at

 

If the fan in your example is running when you test the voltage, and you have a high resistance connection in its supply wire, the voltage at the fan under load will drop and amps will likely rise. The bad connection will get warm as well. Under no load the voltage through a high resistance connection will remain unchanged....same on either side.

 

^ Voltage is proportional to current load. The higher the current load, the lower the voltage will be. Resistance of any kind will effect both current and voltage. This is one reason it's important to have properly sized wires and low resistance connections.

 

you should go help the guy w/ the 4dr '57...take a break from yours!

 

#10 AWG wire is rated for 30 amps. I use 6 volt battery size cables on 12 volt cars. I prefer to make my own using copper welding extra flex cable. After working in a power plant as an electrician for over 45 years I don’t undersized any wiring.
PS: 10 years on a Pertronix USING a ballast resistor and factory hot start without a failure and yes I carry the point system in-the trunk with a pos Chinese condenser.

 

What coil and resistor are you using if I may ask?

 

Why not just increase the wire size from relay to fan?

 

High resistance on the power side of the circuit would result in reduced voltage at the fan and decreased fan speed. Depending on the amount of resistance, the component (wire) would get hot. If you think about it, that is the way they control heater fan speed; with a resistor block. The resistor block gets very hot and is normally located in the heater box where there is a lot of air movement.

 

Fan isn't an issue. It was just an example

 

As said, a resistance in the circuit will cause a voltage drop.

As for electric motors, they aren't particularly bright. The current goes up as an increased load brings down the rpm. The increase of current comes with an increase in torque so you get more work out of the motor, a good thing in moderation but put too big load on that motor and the resulting huge current will burn it. Usually not a problem in a fan as they generally are lightly loaded, and aerodynamics reduce the load very quickly as rpm goes down.

But say you have a rather big voltage drop and an old, tired fan with dried up lube in the bearings. You turn on power to the fan but due to the voltage drop the voltage at the motor is quite low, not enough to get it rotating. The motor is locked up, the current through it is very high, and it burns out soon. Had the motor been fed full battery voltage it would have had enough power to get moving, and once moving the current drops down to survivable levels (even if the bearing friction prevents it from reaching normal speed).

Most times a resistance in a feed/ground line won't damage anything (other than the line if it gets hot enough), but there are times when a reduced voltage prevents things from working normally leading to damage. Another factor especially in ignition systems is that a poor connection in one place may cause some of the very high voltages from the coil to reach other parts of the system instead of (for example) be led directly to ground. Results can be unpredictable.

 

So in the case of my problem with the coil, I have 13.7v coming into the coil which is higher than the 8v minimum, grounds have been tested with zero resistance multiple times, all components before and after the coil test fine or been replaced with known good parts, why is the coil overheating and losing spark? In the example someone gave of the fan motor using resistors to slow the fan down it doesn't overheat the fan motor so, the answer to my original question I guess is that a resistance before the coil should not affect the performance if its input is within normal range.

 

I do not know / understand all what @G-son knows & describes..

I have been following along in this thread you do have a unique situation. Myself ,If I lived closer and had my stock piles of my parts that I have on my shelf like a Speed Shop when you've been doing this for close to 45 years,
.
I know / sounds like you do not have a stock of parts in your inventory like others and I do, I mentioned before and one of the postings

(( I thought post use to have a # ? But I do not see a # Now)

If I was working on your car, I would
Take & ""Disconnect everything"
Meaning , take power supply from Bat in car Now , ""Disconnect the existing ground in the car"

Then I would take a bat or the One you have , Set on floor , Run/attach a positive and ground directly to the starter, Make a Power lead
hook /Connect to positive power to the coil and run a ground wire from the battery to the coil itself / mount.
From coil Negative pole to the distributor. Use a bump remote jumpstart , to start engine ,, Make sure Batt before starting is Fully charged ,after starting I would more likely use a charger set @ 30-40 amps to keep Volts up on bat , start testing , let run ,,
Test & document, Then if test goes well ,
I would keep like test set up,,,
Install another bat in original location just the power light fuel pumps or whatever else is going on in your vehicle that needs 12 V but have it separate than your ignition system and see what you find,,,


If you do not under stand , & someone Else maybe here can explain it to you in a better way if not PM me and I will get in touch over the phone,

Just trying to help , thanking out side of box ,, Yes it would be a lot of diagnostics and troubleshooting, Garb ,,,, but you definitely been working at this for a couple weeks now





If I was working on ,I have 3,4 different distributors, & coils ,The ones you all ready have , , Then a points , HEI , Small Hei , Mallory Unlight ,One of those cheap china $65
Hei , witch I also used for 4,5 years with No problems even on a Engine making
Over 600hp @ 6,700 rpms ,,,
& I also have 6 different Mag ..
Again I know most do not have this many Options lying around..

Also in your example I quoted you mentioned the fan overheating as an example,, The fan itself also cools itself down by having air go across the armature and brushes,

Another thing off topic Not your Issue ,I have done test on this, Many like to use a non-contact temp gun and take temps off the corners of the head or exhaust tubes on cylinder 1 and 3 and 2 and 4 , if using a non-contact temp gun the fan will give you false readings because it's cooling the end / front half of the engine with the air off the fan,
Use cardboard to block the air from hitting /shielding the front half of the engine and you will get a better temp reading from the non-contact temp gun.

 

Well, it affects spark energy slightly, but as you say, as long as it's within the normal range it shouldn't really matter.

I can only think of two things:
Too much current
Current on too long

Too much current would be caused by too low total resistance (a coil ment to be used with a ballast resistor being used without one) or a too high voltage (and as about 14.4V is normal in a 12V system anything below 14.4 shouldn't be anywhere near too high).

Current on too long would be caused by incorrect dwell. As far as I know that's not in any way adjustble in that ignition, probably controlled by the metal part the hall sensor is triggered by in the distributor (I assume these use hall sensors, might be optical or some other technology). Not really something that could go wrong normally.

I'd consider trying a ballast resistor (assuming I didn't have equipment to analyze what's happening in greater detail).

 

Are you checking voltage at the coil with the engine idle or at / around cruising rpm?

 

Voltage is at idle, cruising just going off the gauge

 

After reading most of the posts, here is what I would do if it was mine, and I apologise if it's already been covered. First I would get rid of the one wire alternator and get one with a voltage sensing wire which would go to the fuse box. It senses voltage at the fuse box instead of right at the alternator. It makes the alternator more reactive to voltage drops farther down the line. When you install the Pertronics make sure to use the heat paste between it and the mounting surface in the distributor. If you don't it may fail. Next run a ground wire from the distributor body to the engine block. Then a ground cable from the engine block to the frame, then engine block to the body, then body to the frame. You can never have too many grounds. I even run a ground from the dash to the body. I helps the gauges read accurately.

 

Well it's been a bit since I updated anything. Took some time off from the car to get some other things done before the snow falls, but mostly got away from it for my sanity, lol. Made some changes and thought I was going in the right direction(still think I am) but think I found at least 1 issue and a couple more questions.

I ordered a new flamethrower coil with 1.5ohm primary resistance. Same one I had originally and that was recommended directly from a Pertronix tech. Took almost 2 weeks to get here, mostly I think due to the hurricanes, can't control that. Bummer but not a big deal. Boxes looked new and perfect on the outside, but inside the flap holding the coil was torn and the nipple for the coil wire was chipped or sanded flat on one side. Ohm'd it and got 1.1ohms, same as the "bad" one I replaced from them. I called pretronix and asked if 1.1 was good or bad since it tested the same as what we took out. He said 1.1 is bad and not to run it. Has to be 1.5 or it will have issues. So I called the shop back and told them it looks like I got a bad coil or accidentally got a coil that was returned from another customer that failed. I used to work with a company who sold thru all the major parts suppliers and unfortunately it happens more than you would think. They say they will issue a return label and get me another one on the way when they recieve that one back. It took almost a week and a half to get the label from them. Figured with shipping and processing, it would take almost another 2weeks to get the new coil so just ordered another one and had them credit the return. That gets us to today. Got the new coil and it looks great, no damage. Get the fluke meter out and ohm it and...1.1ohm primary resistance. Same as the "bad" one and the other one I recieved. I tested the ohm meter on some other non-automotive resistors I have around and it measured dead on what it was supposed to, so I don't believe the meter is off. So now I have to email Pertronix again and find out what's going on. I now have 1 failed coil and 2 new coils that all read 1.1ohm. I am wiring in a 0.8ohm resistor inline before the coil to lower voltage as has been suggested here before, and trying to research online it seems 50% of the people who did this had it fix this issue while the other 50% saw no change or it created other problems. So I guess it's worth a shot if the coil resistance is ok. I'm also wiring the module direct to a switched 12v source with an additional inline switch to cut power when needed as I have read being done on many applications, and is wired that way with points from the factory on many 70s and 80s cars. Mostly mopars and ford's from what I have seen. So I should have approximately 8-9v to the coil and full voltage to the module the way it is wired now. Btw, inline cutoff switches have a higher amp rating than the coil and module draw and have been checked for resistance, 0.0ohm. They are good and won't be a problem.

Now in testing the wiring and cutoff switches I accidentally discovered something that is odd and could be the cause of all this or it could be nothing. I just don't understand what or how it's happening.

I was checking the voltage and switches to the coil and module, fluke meter measuring 12.2v at the coil ignition switch on/engine off,flip the cutoff, 0.0v, perfect. Check voltage to the module same results. This was with the negative test lead on a chassis/body ground, positive lead on the +coil terminal for coil test and module test was +lead to the last connection to the module. Same way I have tested for voltage for 25+yrs working on cars. I stopped and looked away, then went back with the positive lead of the meter back on the coil and got 5.87v. I then realized I had the lead on the ground side of the coil! Ground lead of the meter still on the same chassis/body ground! I have this voltage even with the power to the coil turned off and positive wire to the coil disconnected! The ignition key was on. Turn it off, power goes away. A little more diagnosis and I take the tachometer wire off and find I have 5.87v coming from the tachometer to the coil negative. Looking at the wiring diagrams for the pertonix module, the coil and the tachometer itself, the wiring is correct to run a wire from the negative side of the coil to the tachometer, but why do I have nearly 6v coming from the tachometer when removed from the coil negative? The tach was working fine, zero issues. But the tach has its own 12v input. I don't believe I should see any voltage coming from a wire that is going from the coil - to the gauge, should I? The attached drawing is exactly how it was wired.
Now after I saw this and started looking at the gauge wiring noticed another issue, the speedometer and tach are in the same gauge(2in1 unit) when looking at the speedometer wiring diagram, the signal from the vss and the signal for the tach from the coil negative both go to the same input? Like I said, the tach has worked fine, and the speedo works but does bounce around once in a while. I do not currently have the speedo and tach on the same input , so tomorrow I have to pull the gauge and see how the speedo is wired, but the tach is 100% wired like the diagram. I may try to start and idle the car tomorrow with the tach wore disconnected to see what happens and monitor everything else to see if I still have the same issues or if it's working properly. I know when the car was not starting, I disconnected the tach wire to see if it was causing the no-start issue as it was suggested by someone to check. At that time it made no difference with the no-start issue so I reconnected it.

I am sorry this is so long again. Just trying to get the details. As I said at the beginning, going in the right direction, but more questions if you have any ideas about the tach voltage issue, let me know!

Thanks
Mike

 

Also, for those that have been asking/suggesting the alternator, in this downtime I removed the alternator and took it to Speedometer Service (e1956v from the site vendors) who originally built this unit for me and he checked it all out. Pulled it apart and checked the diodes and other internals. Zero leakage on the diodes and great on the oscilloscope. He knows all the details about it, i just bolt it on and go, lol. All I know is it's a badass unit that will do everything I would ever need it to without issue! Great products, great service! Thank you!

 

Well again if you made it this far I am sorry for the long previous post. Went to fire it up today and no spark again. With an inline spark plug checker, it would spark one time everytime the key was turned off then tried to crank again, only one time. Went and bought a new ready to run points dizzy from O'reillys, installed and rewired again. We have spark! After a couple tries trying to dial in the timing some it fired up and idled great. Ran for 30-45 min, coil has 11.5-12v going to it now with the inline resistor and only reached about 160° in that time. I think we have a winner. Seems in burned up another pertronix module in about 1.5-2hrs drive and idle time. If the weather holds out next weekend I'll take it for a longer cruise again and see how it does.

My main question now is still the 6ish volts I have coming from the tach signal terminal of the tach to the negative side of the coil. Currently I do not have the tach wired up, but could this be what burned up the module? I have cut off switches on the positive side wires to kill power to the coil and module, but didn't think there would be voltage in the negative side. Maybe this is normal for electric gauges? Idk. If the car runs and checks reliable, not having a tach right now is minor. I'll see what happens in the next 400 miles.

Thanks to everyone in this thread offering ideas and suggestions!

Any ideas about the tach voltage are welcome

 

Finally! I have read mainly bad things about Pertronix products.

 

More than just a few times I have seen a tach cause ignition problems. I've unplugged them and problem solved.

 

I’m lazy when it comes to reading, so I’m not sure if this has been covered. If it has just disregard. Are you using a Pertronix Coil?
I have never had an issue with Pertronix performance, but I know many who have. They all were running non Pertronix coils. Just my 2 cents.

 

The one supplied from Pertronix and the stock replacement one for a 1956 Ford.

 

Negative wire voltage at coil when power is off.
What is voltage at tach with power off?

 

It is not uncommon to have voltage reading on negative wires coming out of devices if they are not properly grounded or you check the voltage prior to the final ground. The problem you have is the the negative post from the coil should not go to the ground on a tach. The voltage feeding in the negative post on the coil is reducing the effective voltage the coil has which causes your coil to over heat and is most likely the cause of your problem. Notice in the diagrams you posted, the coil does not go to the tach ground. It goes to the signal input wire. The ground is separate on the tach diagram. You would need to ask the tach manufacturer, but there should not be voltage back through the signal wire. So you either have the coil wired to the tach ground, or the tach isn't working 100% correctly.

Edit: Try unhooking the tach and then drive the car and see how it does. Double check the actual ground wire to the tach and make sure it goes to a ground.

 

I wouldn't worry too much about a voltage backfeed from the tach sense wire, at least not measured with a modern digital multimeter - those are VERY sensitive and may give a high voltage reading in many situations despite a high resistance is in place preventing any significant current to flow.
If you want to test that, put the meters negative wire on the 12V car battery negative, hold the positive wire between the fingers on one hand, and touch battery positive with the other hand. The meter will probably show close to full battery voltage - wet your fingers and you'll get even closer. You see a high voltage despite measuring through your body that doesn't conduct electricity very well.

In a case like this I'd disconnect the tacho for a while and make sure it isn't a factor in the problems, simply because they are a common source of ignition problems, when they let too much current through from the signal wire.

 

So surprisingly I already recieved a response from Pertronix. They said absolutely do not run the coil if it reads 1.1ohm as it is a faulty unit. That makes 3 flamethrower coils p/n 40111 bad out of the box before they were even installed and connected to any wires. So I don't know what to do about that. They also said I cannot add an external resistor before the coil. Didn't specify why?

Pprather and snoc653

The 6v is in the wire going from the coil ground to the tach signal wire. Not tach ground. This is with the key in the run position only. When key is off no voltage.

As suggested for now, the tach is remaining disconnected until I can try to get more info from the manufacturer. In the little time it has ran, I have noticed no difference in how it runs with the tach disconnected. That again is why I am curious if it's even a problem. I will try to find another coil with 1.5ohm primary resistance, but there is no longer any local performance shops so I'm guessing it's back to summit or speedway. If the weather is nice this weekend I will put it all together as is and drive it just to see if there is improvement at all.

 

It seems pretty strange that you've gotten that many Pertronix coils that are bad. I wonder if someone has slipped some counterfeits into the supply chain. MSD had that sort of issues a number of years ago, maybe they've moved on to them. I'd try ordering direct from Pertronix to see if that clears the problem.