Ignition Coil Overheating

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C

CheeseWheel

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Let me just say first off that electrical problems are probably my worst at fixing.

With that said my 74 Duster (225) was running great until it started acting up. The car would crank fine and function swell until a few minutes into being crank the coil would overheat. After that point the car would hardly idol and once to hot not crank. Of course waiting for the coil to cool down allowed the car to crank once more and run until the coil overheated again.

I figured it was just a faulty coil causing the problem. So I replaced it to find that the new coil is also overheating but not as quick or hot as the old one. It seems to overheat more when the car is in drive.

The ignition system functions off of an electronic distributor so it isn't points which crossed my mind before checking the distributor. The reducer is hooked up as well.

Could it be a faulty reducer? or is there a special place in the wiring I should check? Perhaps groundich or something?

There seems to be some sort of small ground like piece on the coil bracket. It is maybe the size of like a c battery with a short wire coming from it that has black to signify negative I believe. This is not hooked up. It wasn't when I got the care and like I said it was running fine. Should I hook it up (to negative)?

Also the reducer was not hooked up as well. I hooked it up after the care started having trouble. It was all there just not hooked up (plugged in). Could it be that I plugged the wires in backwards or something?

The coil certainly calls for the external reducer. It is a oil filled coil I purchased from Oreily. The previous coil was as well oil filled and called for the external reducer.
 
I don't know what you are calling a "reducer". Maybe a "resistor"? It sounds to me like your circuit is keeping 12 volts on the coil past the point that the car cranks and starts. At that point, the circuit switches to the resistor to reduce voltage at the coil plus side to 8 or 9 volts IIRC. Check the voltage at the positive side of the coil with the engine running. If it's 12 volts, then you've confirmed the problem. Then start looking at the ignition switch.
 
The noise filtering condenser is your "battery" like item which should reduce noise on your radio. This diagram may help you...
Not sure what changed in the 74 Duster from this if anything.
vbpgimage.php
 
I meant resistor. Vocab isn't one of my strong points sadly and been one of those days. Anyways, I'll check into the voltage and get back with you guys on that. Thanks for the input and the diagram guys.
 

Canister coils always run hot. Almost too hot to touch.And hotter when they're screwed to the engine.And that would be normal.
I think she may need a valve-adjustment.and a starter.
Is there coolant in the block?
 
What electronic distributor do you have? The stock Mopar one?

Your resistor is called a ballast resistor. It wired in between the 12v supply from the ignition switch on one end, and to the coil + on the other, when the car is running normally and the key is in RUN. But when you turn the key to START, there is another wire that carries 12v directly from the ignition switch to the coil +; that bypasses the resistor temporarily when you are starting. It is the 'start bypass'.

It may be that the wiring is messed up and the start bypass is on all the time when running, and that will indeed overheat the coil. The best way to check this is the get a voltmeter and check the voltage on the coil + when running. If it is in the range of 6 to 9 volts, then things are normal. If it is 10-11 volts or higher, then the resistor is improperly bypassed in the RUN position.

Let us know if you need more info on how to use the voltmeter. Get one, as it will be your friend on this vintage of car.
 
1....You may be imagining the coil is running hot, or may actually have a problem


2....Measure battery 'running' voltage. It should be about 14V depending on battery charge and load on the system. If the system voltage goes very much above 14, and certainly above 15-16, you have a big problem

3....If the voltage at the battery is OK, clip your voltmeter to the coil + terminal, start and run the engine at various RPMs for a few seconds. This voltage should vary from something around 8-12V and no higher. If the battery voltage in "2" is OK, but the coil voltage is quite high, 13-14, you have a problem, wiring, or wrong ballast resistor, or someone bypassed the ballast resistor

4....See if you can deterimine "what" the coil is. The coil may be the wrong coil, not compatible, or it might have a problem (partial internal short) Look for part numbers on the coil, brand name, etc, or see if you know or can find out "where it came from."
 
I didn't have much time this evening to really check into things but I looked at it a little bit. It seems that the voltage was reading the same both when the key was turned on and when the car was cranked. If I have more time tomorrow I'll check into the exact voltage (getting to be a busy time of year for a butcher).

I did notice that the hot wire when the key was turned on seemed to be the wire that was hooked up to the (-) primary terminal. I thought that the hot wire should be hooked to the (+) primary terminal. Would that be correct? or will it function no matter how the primaries are hooked up? I hooked the new coil up the exact way the old one on the car was hooked up. After noticing that I then readjusted the wires so that the one getting fire when the the key was on and neither were hooked up to the coil so that the one being fed fire was hooked up to the (+) labeled primary terminal. If that is wrong I will switch the two back. Even after doing so the coil still heated and the car began to cut up once more. It runs perfect though until the coil gets extremely hot.

I also forgot to mention early that the person who had the car before me did infact mess with the ignition switch. They seem to have removed the wires from the initial key switch to a single targa switch and push button setup.

I'm starting to think that perhaps this setup was done incorrectly so I am going to check into that more.

The coil that is on the car as of now is brand new from ORiely's. It is the coil their computer system called for. I would have to think that it is hands down the right coil; however, I will also check more into that as well.

And I am pretty certain it is the coil or something along those lines. Like I said the car runs perfectly fine until the coil gets just God awful hot. Then let the coil cool down and it cranks and runs perfectly fine until it gets hot once more.

I'm not sure exactly what kind of distributor it is. All I know is that it is electronic. I'll try to look into that more and give some more details on that subject as well.

Thanks for all the help so far. You guys are awesome. I know some of my questions may come across as ignorant to the fact or clueless but just hang with me if you would. Really appreciate the patience.
 
With that switch, "anything" could be goin' on. Post the part no of the coil they gave you. We need to figure out just what you have for a coil and ignition system. Photos might help. Might be a Mopar breakerless, a Pertronix conversion, or one of the several "no brand" "ready to run," who knows.

The problem with aftermarket switches like that (if it bypasses the factory ignition switch) is that on Mopars and ONLY Mopars, the coil resistor (ballast) bypass circuit is done right in the ignition switch.

On Ford/ GM cars, it is done at the starter solenoid, and on the GM HEI cars, there is no resistor

So if your ignition DOES still require a resistor (probably does) you need a bypass circuit for starting. Depending on what this extra switch is, and how it's wired, there are a number of ways you can "get around" that. One is to parallel a bosch relay with the starter relay so they both activate together, another is to use the later model Jeep starter relay which has an extra contact, and still another is to use a big diode to run the bypass.

FIRST we need to

Figure out your switch wiring

Figure out just what this ignition system is you have

And the coil part no.
 
CheeseWheel said:
I didn't have much time this evening to really check into things but I looked at it a little bit. It seems that the voltage was reading the same both when the key was turned on and when the car was cranked. If I have more time tomorrow I'll check into the exact voltage (getting to be a busy time of year for a butcher).
Click to expand...
Getting the voltage reading would be good. Your description of the wiring does indeed sound like it is hosed up.

If you have not down so already, download your car's wiring diagram from mymopar.com. It wil be invaluable.

You can reward us with some prime cuts LOL!
 
A small data point re "coil too hot". When driving my 64 Valiant home after purchase, it instantly flamed out. I found the key switch was gomer-wired with individual spade terminals and other hacks, so hot-wired coil+ straight to BATT+ w/ a jumper. It started right up and ran fine for 5 min, then started missing bad (bucking) as I tried to accelerate past 45 mph. Did that several times. The coil was so hot the paint was starting to melt and smell. That is "too hot". As mentioned, yours might be "normal warm". I then wired jumpers thru the ballast resistor (~0.5 ohm) which the factory put there for a reason. Drove the remaining 70 miles home with no problems, other than the clunky rotted bushings and such.

Get a multimeter and measure from the engine block (blk) to coil+ (red). Should be ~8 V while running and full battery voltage while cranking (bypasses ballast).
 
I had time today to mess around with the voltmeter today and get some clear runnings on several different key parts mentioned in the topic. I hope it is helpful.

I also have the name and part numbers to the coil: MasterPro (on box# 2-5195/on bottom of coil#01301)

The battery when not hooked up read 12.87 volts. With car running read 14.58 volts.
The coil when not installed into the car read 2.20 ohms at the primaries and 9,660 ohms at the secondary.
The coil when installed into car and key switches turned on (both ignition switch and toggle switch) but car not running read 11.06 volts (a volt and some shy of what the battery read), with the car running the coil read 14.13 volts (.45 shy of what battery read with car running which I believe as stated before by you guys should not be), and then I turned off the toggle switch leaving the original ignition switch in the run position (which it sometimes keeps running while doing so and sometimes dies) which read 9.40 volts (I believe that is much closer to what it should be reading).

While I was there I went ahead and checked the ohms on the resistor and pick-up coil.
The resistor read 6.0 ohms on the top two prongs and 2.5 ohms on the bottom two; I think those are good readings but I could be wrong.
The pick-up coil read 439 ohms; I think that is low.
Of course I tested both of those while they were unhooked.


It is certain to me that I need to fix the wiring issue with the ignition switch, but I wonder if I should also go ahead and replace that pick-up coil as well.
It is my understanding that the resistor is a dual resistor which protects both the coil and pick up coil from overheating due to to much voltage being passed through for an extended amount of time. I could be wrong there but I believe that is the simple function of it. So is it possible that the pick-up coil has gone bad from overheating over time and this is what is causing the car to start to run like crap after a few minutes and eventually die to only crank again once things have cooled down?

I didn't see a part number or anything on the toggle switch. All I can say is that it looks similar to that pick I posted. I'll try to use my wife's phone to take some pictures of the set up he has rigged up and show you guys. If possible I'm gonna try to wire it back into the original ignition switch as it seems that it was dropping the voltage on the coil in the run position.
 
You are off track on the pickup coil, here is the deal on the dual resistor. Refer to this simplified diagram

Ignition_System_5pin.jpg


The wire at far top right is "ignition run" labled "existing wire." This is hot from the ignition switch in run

What is NOT shown here is the brown ballast bypass starting circuit, "IGN2" which comes from a separate contact on the ignition switch, and goes to the coil+ side of the coil for starting.

The RIGHT side of the resistor is the exact same circuit as the old "points" circuit, that is, ignition voltage from the key, through the ballast, through the coil, through the points, to ground.

The only difference in this part of the circuit, is that the box replaced the points, switching the coil NEG on/ off

Now this "5 pin" ECU with a "4 pin" resistor is the old design. The LEFT side of the ballast still gets voltage from the ignition switch, down through the left side, and powers the box. THIS RESISTOR was eliminated in later designs, resulting in the "4 pin" ECU, with "2 pin" resistor, below:

Ignition_System_4pin.jpg


Most any ECU you buy is going to be "4 pin" whether it has 5 physical pins or not. The 5 pin box MUST have a 4 pin resistor, the "4 pin" ECU can use either 2 or 4 pin resistor.

===========================================================

Your coil+ readings during "run" are high. If the wiring is not "hacked up" you may have a problem with the ignition switch. It may be feeding power (wrongly) through the brown wire to the coil in the run position. That brown is supposed to ONLY be hot in "start."

How to find this? Try this:

Get the car running, and confirm that you have too-high voltage at the coil. Find the connector on the ballast which has the coil + wire and the brown wire. Pull this off at the ballast. If the car keeps running, there is a problem in the brown wire circuit. Most likely is a screwed up ignition switch.

Does it seem like the wiring is factory, or has it been hacked up some.
 
Most any ECU you buy is going to be "4 pin" whether it has 5 physical pins or not. The 5 pin box MUST have a 4 pin resistor, the "4 pin" ECU can use either 2 or 4 pin resistor.
Click to expand...
On a 5 pin ECU ohm the 5th pin to the case & if it has no continuity then what Del said, it is a dummy pin & you can use a 2 terminal "single" or a 4 terminal "dual" ballast whereas an OE 5 pinner has a live 5th pin & requires a 4 terminal "dual" ballast. this is the pin under the red/green wire in the pentastar plug in ECU connector, the ~4 o'clock pin position in the diagram which goes to the lower left terminal in the 4 terminal "dual" ballast in the pic. With a 4 pin or a dummy 5 pinner ECU you can connect both ends of a 4 terminal "dual" ballast across side to side with blue loops like the one blue loop that is OE on one end & run a wire in/out to each end like a single ballast. this converts the 4 terminal ballast to a 2 terminal ballast & the last one I did gave me 1.1 ohms which is is pretty close to your needs (depends on your coil). Need at least 1.5 ohms (coil+ballast total). #1 what coil are you running then adj the ballast.
 
CheeseWheel said:
........... MasterPro (on box# 2-5195/on bottom of coil#01301)

The battery when not hooked up read 12.87 volts. With car running read 14.58 volts.
The coil when not installed into the car read 2.20 ohms at the primaries and 9,660 ohms at the secondary.

The pick-up coil read 439 ohms; I think that is low.
.
Click to expand...

I intended to comment on this and forgot

The factory coil resistances are in the shop manuals. You can download many of em at MyMopar. The reading of the pickup is OK. That reading is not critical, and if the car will run the pickup is OK. The resistance of the pickup is not critical, probably anything from 200 on up to 500 somewhere is probably OK, and it MUST be infinite to ground.

Below is a shot out of the 73 shop manual, section 8, "specifications." Seems to me your replacement coil is "reasonable."

6xx4xu.jpg


Note the two resistances listed for the ballast. The "U" shaped cutout in the ceramic is to index the ballast so you get the "correct side" hooked to the 'correct side' The lower side is for the coil, the "aux" is what powers the box

We at least can assume that yours is hooked up correct, because otherwise the coil voltage would be quite low. By the way, this "high" coil voltage you are seeing...........you ARE measuring this "right on" the coil PLUS terminal?
 
I understand you should never leave the key switch in "run" with the engine off, except very briefly to make a quick measurement. Otherwise, it is said to sometimes kill the ECU. Surprised 67Dart273 didn't let you know.

Coil+ definitely shouldn't be 14.1 V while running. I am sure the coil will soon get too hot to touch and the paint start melting. It could also damage the ECU. The bottom ballast resistor should measure ~0.5 ohm when cold, but that is a tricky measurement. Short the DMM leads together and subtract that "zero reading". The top resistor should be 5 ohm, but as said most replacement ECU's have a dummy 5th pin, in which case that resistor does nothing.

Most likely your IGN (blue) and IGN2 (brn) wires are shorted together. Unplug the ballast and measure. If you measure that w/ the key off, it is likely in the wiring, but unplug the column connector to verify. If in the wiring, it would most likely be in the bulkhead connector. They melt from the high alternator current run to the ammeter and cause many problems.
 
67Dart273 said:
Sorry, and I ain't blamin you but those guys are full of "it."
Click to expand...
IMO, and im pretty smart, if you are using the right coil, designed to run on 12volts and running a ign system that runs on 12v you dont need resistor. No points, the reason of the Ballast was first and foremost to keep the points from fusing. the added benefit was the manufactures could use cheaper coils, And they did. I am using a blaster coil with ballast bypassed, a cheap china electronic dizzy, works good, no heating issues. And while I would not pretend to more versed on electronics and wiring then the Guru himself, ^^^^, The issue of the ballast resistor has always been a gray area. Real simple in a stock setup. Who has a stock setup?:burnout:MT
 
The article that Mopar_Tim linked was at least written quickly without detailed thought.

Ex. "needing a ballast resistor to control amperage through the pickup coil."

Did they really mean to say the ballast is in series with the distributor's pickup coil? I am sure they meant "primary coil".

Tim is right that there are likely many after-market combinations where a ballast isn't required. One is if you have a "ballasted coil", which has internal resistance which replaces the coil. I think Mopar used those in the 1978-88 era (lean-burn & such) since I have one stamped "for use with electronic ignition only" and recall it has the Mopar pentastar. The article implies those cost more than a low-resistance coil (~0.5 ohm) plus external ballast, which is why the factory chose external (unlikely). The factory surely used an external ballast on the firewall because that allowed easier wiring to bypass it when cranking and run only one wire across the engine to the coil.

The 1970's Mopar ECU had no "dwell control". A ballast was needed to prevent over-heating. Many early after-market ignitions still required keeping the ballast in. The Crane Cams XR700 I put on my 65 Newport vaguely said to keep it. I ran for years with the ballast bypassed and never noticed the factory coil over-heating. But, one driver box finally failed and I had driven only 1/4 mile, so unlikely it was hot. Might have been unrelated, and much after-market stuff is unreliable. Luckily I had a spare Crane box in the trunk and spark tester, so quickly diagnosed and got going again.
 
Mopar Tim said:
IMO, and im pretty smart, if you are using the right coil, designed to run on 12volts and running a ign system that runs on 12v you dont need resistor. No points, the reason of the Ballast was first and foremost to keep the points from fusing. the added benefit was the manufactures could use cheaper coils, And they did. I am using a blaster coil with ballast bypassed, a cheap china electronic dizzy, works good, no heating issues. And while I would not pretend to more versed on electronics and wiring then the Guru himself, ^^^^, The issue of the ballast resistor has always been a gray area. Real simple in a stock setup. Who has a stock setup?:burnout:MT
Click to expand...
I do.... a 98% original '62 Dart LOL. And my son's '65 'Cuda has a ballasted coil with Mopar ECU.

Actually, the points fusing is not the reason for the ballast resistor; points fusing, contact erosion, and transfer of metal is what the condenser prevents. The ballast is a simple form of automatic current regulator, and allows more current to flow in the coil, and thus generate more spark energy, during the first 30-60 seconds of warmup from a start. (Not during cranking, as it is bypassed, to compensate for lower battery voltage while cranking.) It also allows more current to flow at high operating RPM's to compensate (to some degree) for the small dwell times that will lower spark energy at high RPM's.

The coil current is the same with a non-ballasted 3 ohm coil versus a 1.5 ohm coil and a warmed up OEM ballast so no difference there.
 
By looking at the wiring under the dash it seems he spliced off of the wiring going to the ignition switch to install the toggle switch and push button set up.

I'm try to track it all down under there and set it back the way it was removing the toggle switch ignition. Like I said before with the car running if you cut off the toggle switch and leave the ignition switch itself in the 'run' position the current drops to around 9 volts at the + terminal of the coil, while running.

The car at the moment can not be cranked without the toggle switch though as it seems the wire going to the starter is strictly tied into that setup. The ignition switch on the steering column will not crank the car. I'm guessing fire/wire going to the 'start' position has been disconnected.

I'm hoping that after I get that wiring redone it solves all the issues.

Is there anything else you guys can think of that I should keep in mind while or after doing so?
 
nm9stheham said:
I do.... a 98% original '62 Dart LOL. And my son's '65 'Cuda has a ballasted coil with Mopar ECU.

Actually, the points fusing is not the reason for the ballast resistor; points fusing, contact erosion, and transfer of metal is what the condenser prevents. The ballast is a simple form of automatic current regulator, and allows more current to flow in the coil, and thus generate more spark energy, during the first 30-60 seconds of warmup from a start. (Not during cranking, as it is bypassed, to compensate for lower battery voltage while cranking.) It also allows more current to flow at high operating RPM's to compensate (to some degree) for the small dwell times that will lower spark energy at high RPM's.

The coil current is the same with a non-ballasted 3 ohm coil versus a 1.5 ohm coil and a warmed up OEM ballast so no difference there.
Click to expand...
See what I mean? I agree with some of this, it is a gray area. How would a resistor change its value just because the engine is operating at a high RPM? I get how it changes value as it warms up.
 
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