Hey all, I am NOT an electrical guy, hell, I am barely knowledgeable enough to be a car guy. '49 Ford shoebox. Ran fine the first few years we had it. was converted to 12v by previous owner. I rewired it (rebel kit from Shoebox central, rebels customer support was/is awesome), just to get brighter headlights, working turn signals front and back. All that was fine, car ran fine. I had a gauge issue and while troubleshooting it one day I left the key in the On position and burnt up the coil. No joke, I was standing at my workbench when I saw smoke, turned and smoke was coming out and oil/fluid. No problem, replaced the coil with same, made sure it had an internal resistor (car didn't have an external one that I could find, replaced the points to be sure. Just cheap basic napa stuff. Here I'll say the car is me and my brothers, so I am trying to get the timeline right. While driving it my brother had the coil burn up again. Just while driving. He replaced it with another "6v coil) I didn't know that they came in 6 or 12. -after running it he "realized it was a 6v and should have a 12v coil" -he put on a nice Edelbrock coil, that one he noticed the coil got hot because he saw oil coming out. -replaced with another edelbrock, and filed the points -then it was running and was sitting at idle no problem, but under acceleration it started skipping, then it started running alltogether. There is a car show tomorrow, only thing I can thing we can think of right now is to replace the points. Ideas what could be going on? Can I ask a second question or do I need a separate thread? On the gauge cluster, I have power and ground at the gauge cluster. none of the gauges work. Is it possible all the sending units would be bad? I plan to get a cheap gas gauge/sender and just wire it up and try it, but wonder if there could be some other root cause I'm overlooking. Red PS we bought this when our uncle was alive, he had all the knowledge and the shop. He died and the whole thing became exponentially more difficult. Especially since most of our friends aren't car guys. so I ask stupid questions here.
Your second question is probably related to your first question. All gauge sending units being out doesn’t seem likely. Sounds like something is grounding out.(?)
Almost every 12 volt coil has to have a resistor to survive. GM used resistor wire, Mopar used a ballast. You didn't mention what engine/dist. Here's more talk. https://www.jalopyjournal.com/forum/threads/ballast-resistor-or-not.398528/ I would suggest wiring in a ballast to the feed side of the coil and trying it. Bring a thick jumper to bypass it if you want to be safe. After burning down a couple coils now, I would make darn sure you have a fire extinguisher. I'd also dive into the wiring to check everything, especially ignition on circuits. Gauges, you didn't say if it's mechanical, electric or both and what they are. Always confirm a good ground. You will need this for electrical gauges and any lighting. Mechanical should be temp so you can heat it and see if it changes. Hot tap water will do it. Oil pressure, check the tube or hose. You can apply air pressure to this if you have a compressor. You don't have to have a tight seal, just blow in enough to move the needle. Fuel is always electric. It requires good power, then the sender changes resistance depending on level. Search for expected Ohms resistance range, they are different on brands. Oil and temp electric is the same, power in, sending unit varies resistance to ground depending on what's happening. Most also have a ground too. EXAMPLE I= ignition GND = ground S = sender
That is awesome!!! Thank you RodstRace. I think you are onto it with the coil!!!! The original coil was a 27290 (found a pic) which online says 12v and it said on to use with external resistor. I don't remember if it did have one, and I stopped using it because I bought one with internal (knowing nothing), or if I couldn't find one on the firewall and bought a coil with internal to be safe. My brother just bought a 12v coil had no idea anything about resistor. It has the 8ba 239 flathead. we have no idea about the distributor. Should we replace it? I will dive back into the gauges now that my back is recovered enough for me to bend etc. What I remember from checking power and ground at the time is they are all very good. but I don't know anything about ohms. As soon as I get this thing running I should be able to bring it back to my house and start troubleshooting again. The gauges (after it running) are the last thing I have to deal with and electrical can be checked off (until we add a sound system etc.)
Red, one problem at a time...get it running I understand the coil burning up when the ignition key is left on. Coils do not like continuous voltage to them. If you think about the engine when it is running, the distributor is operating the breaker points, opening and closing them. The coil is powered intermittently...but it still gets hot with the key on and the breaker points closed, the coil is powered continuously. Did you ever get the car to run after the coil burned up the second time? If you replaced the breaker points and they never opened, due to improper gap, it would be the same as leaving the ignition key on. That may have taken out the second coil. I am also guessing that maybe you burned up the condenser too when the coil burned up... and that could be why why the second coil burned up. Replace the points and condenser at the same time. your distributor is probably fine...just replace the internal components...points and condenser very point gap...you have to have the follower on the points at the top of a cam lobe to gap the points. tighten the screw and recheck the gap. good luck
Just a case of try it (resistor). If it doesn't need it, weak spark (no damage, real obvious). If it does need it, good spark without burning up another. I don't know flathead stuff like others here. I'd look at the points carefully, and the condenser also probably wasn't happy with a long on, not running abuse. Lots of parts store failures with stuff that's hit the shelves over the past decade or two, so don't assume new = good. I agree with @winduptoy but I'd look things over before diving in, getting it running and going around the block.
Coil polarity has to match the polarity of the battery, no exceptions. Quite often if you get a project car without a battery that is how you tell the correct polarity of the battery by looking at the polarity of the coil. Leaving the ignition on while piddle potting around on the car without disconnecting the coil will fry the coil and is probably the number one cause of fried coils. Excess resistance down stream from coil either in the primary or secondary circuits is hard on coils especially in electronic ignition like HEI.
There's really no such thing as a '6V' or '12V' coil. The actual difference is in the coil primary resistance as measured across the + and - terminals of the coil. If the primary resistance around 1.5 ohm, that would be used on a 6V system OR on a 12V system using a ballast resistor to drop the voltage while driving. The resistor is bypassed when starting for a hotter spark. The ballast resistor ohm value should be about the same as the coil primary. This is the most common setup on an OEM 12V points ignition system as well as some electronic ones. If the measured primary coil resistance is about 3 ohms, that would be used on a 12V system without a ballast resistor. These aren't so easy to find but they are out there.
If you ran the 6 volt stock gauges on 12 volts you may have fried them. To run 6 volt gauges on 12 volts you need a voltage drop to drop the 12 volts to 6 volts.
Personally I think it’s odd that you are frying coils. This seems odd to me. In my experience it’s been the points burning, not the coil with the switch left on and no ballast. I think it speaks of a possible significant issue in the wiring. Maybe it’s a bad ground or grounds? Maybe it’s too small of wire with a poor ground? Too small of wire and poor grounds can cause heat. Maybe it’s a double feed or a dead short somewhere that has been wired in? Burning cools like this is odd. You need a ballast on ignition hot. I prefer to wire a 6-12 conversion in the simplest way possible. On a ‘50 Ford I set it up like the factory 6V system. Example...... Ignition circuit..... Push button goes to solenoid for crank. The key switch to coil goes through a ballast. It’s wired like a 6v system, there’s no need to wire in 12v ignition hot on start. With your original ‘49 key switch there is no start (starter/full 12v boost no ballast). The start is done by the button. The 49 key switch is simply on and off, there no place for 12v start. If you have the original 49 key switch wired like a later switch with the start position, it’s getting a full 12v all the time. Again, I prefer to wire a12v conversion just like a 6v but through a ballast wire or block for ignition hot. There’s no need for the 12v boost on cranking. I hope that made sense.
Gauges..... Fords used King Seely 6v gauges through the 1990s on some vehicles. 1956 is the only year Ford used true 12v gauges until the EFI/ECM era. The 1956 gauges proved problematic. In 1957 + Ford went back to the 6v King Seelys through one voltage reducer on the gauge cluster. This reducer is found on the gauge cluster of late 50s through 80s Fords.
The coil getting hot enough to puke oil should only come from too much current running through it for too much time. How that happened when the ignition was left on a long time is probably self-explanatory, current running through it all the time rather than just when the points are closed short periods as the engine runs. The same happening when running is more likely caused by a too low resistance in the coil primary winding and the ballast resistor in series (if used). I believe 12V coils for points ignitions usually have a total resistance around 3 ohms, that can be a coil alone having 3 ohms, or a coil having 1.5 ohm together with a 1.5 ohm ballast resistor, or any similar combination. Can't see any other sensible reason for coils to overheat and puke oil like that, except possibly if the voltage that feeds it is far above the normal ~14V. If that was the case you would probably also be popping a lot of light bulbs and your battery would soon be very unhappy. Seems far fetched.
Years ago I fried a series of coils (aftermarket Accel coils). One happened at a car show with an Accel booth. I pulled the fried coil off and hiked it to the booth. To their credit, they replaced it on the spot for free. I explained my problem (that was the 3 or 4th coil). In his infinite wisdom, the guy in the booth told me I either had not enough resistance, or too much resistance. He handed me a ballast, and told me to put it between the ignition wire and the coil plus side of the coil. He said if the coil went bad again, I needed to run a new wire from the ignition switch, with the ballast he just gave me before attaching it to the plus side of the coil. If it didn't fail again, it was because it needed more resistance then what was there. That was the last coil I burned up. So, my words of wisdom are, add a new proper resistance ballast between the ignition wire and the coil plus side of the coil (in addition to what is already there). If the coil fails again, replace the wire from the ignition switch and include the proper ballast resister in line, to the coil plus side of the coil.
On My Model A with a Y block, I also burnt up a couple of coils. The car has been on the road for 11 years now and the first coils burnt up about 5 or 6 years ago. It never expanded or pushed out the oil, it just got to the point that the motor would not restart after a long run. Once I found that there was no or weak spark. This was a new coil when I put the car together, NAPA coil with internal resistor. Before the coil went bad I had beed doing a little carb tuning so there was some start, stop, engine stall, restart stuff going on and also some key on with engine off time so I figured this is what did the coil in. Replaced the coil and all was fine. The replacement coil only lasted about a year or two and it failed the same way, just weak spark and engine was hard to start. This time I installed a ballast resistor and a coil that does not have the internal resistor. I also wired up the starter circuit so that when cranking the starter relay would by-pass the resistor. The system has been working fine for the last few years and it seems that the hotter spark when cranking gets the engine started easier.
I don't think positive or negative ground makes any difference with the coil failing. You do have to connect the coil primary the correct direction. If you don't I think it will work but have a weaker spark.
I definitely need a ballast resistor. Maybe that was my bad in wiring the car, I couldn't identify one, and because I am dumb I thought an internal resistor on the coil (when I replaced it, like I said, car ran fine for a while, it didn't kill that coil till I left ignition on). The coil on it now is an edelbrock PN22746, it says. .7ohms internal resistance. do I need one with no internal resistance if I run a 3ohm external? I ran into a buddy at the car show Saturday who said if I run an external I need a coil with no internal. We have a complete distributor rebuild kit from shoebox central that has the condensor, I am going to try to do all of this on Saturday (if I get the external resistor in time, and different coil if needed). Thanks Winduptoy about the information on gapping the points, I um, honestly don't remember if I did it the first time, and I definitely did not include anything about it being on the lobe. Sorry guys, you are dealing with someone who despite not being past 50, has memory issues. when I rewired the car I put voltage reducers on all the gauges. I managed to get the cluster wired up beautifully just like the pics on shoebox central's website. HOWEVER, the car came to us converted to 12 volts, and the wiring was a rats next, nothing was ever pulled out, it was all just added to over the intervening years and was an absolute hell hole. It is possible the guy had wired it up to the gauges, possibly he fried them. I am trying to parse through everyones responses, I appreciate it very very much. If I don't reply to each one I apologize, I'm trying to go item by item. For the starting, I did leave that same as original, key for ignition is on, starter button to start it. We didn't do that because we knew it mattered for function, we did it because overall we want to keep the function and look as original as possible, while making it better driving (i.e. we upgraded the front end suspension parts and added front disc brakes). Right now the plan of attack is -add the voltage resistor, -replace the coil if I need one with no internal resistance (by the way, I thought I felt a little oil around the top of the coil, my brother said it had just gotten hot. I have not talked to him in person in a couple weeks, I am not sure I relayed the series of events correctly on coil vs points damage each time, between each incident though the car ran. He had problems with the points each time. I don't know if that would end up causing problems with the coil though.) -rebuild the distributor -put hula girl on the dash Red
https://www.npdlink.com/product/resistor-wire-ignition-coil/101401 https://www.npdlink.com/product/ign...products?search_terms=Coil&top_parent=0&year= I much prefer the resistor wire. Those porcelain blocks...... Ehhhhh. I had trouble out of them. They get hot, they don’t like wet and in my experience they may need to be changed out regularly. You’ll have figure out how to install the wire if you go that route, splice or use the factory style bullet connections. Just don’t cut it in the middle thick part.
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