Almost burned up

I finally took my 1967 sherries one roadster out for a drive. My friend and I changed the coil because the factory coil did not seem to be providing enough of a spark. So while I was driving I noticed smoke coming out from behind the center Dash instrument panel. I pulled over and it seemed that one of the wires going into the ignition switch was super hot and it melted. I did change the coil today and was wondering if that could have been the culprit. I will upload pictures of the coil box and the wire that got hot. In the picture at the water that is disconnected is the one that got hot.Any help would really be appreciated.

This may be a coincidence.

I would first check the resistance of the old coil and of the new coil. One expects 3 or 4 ohms on the primaries

But your new coil works to provide spark as you could drive the car.

So I would check that all the female connectors that slide onto your ignition switch need a very firm pressure to slide on and off and are not loose.

If they are loose, there would be arcing which would cause heat and melting.

What I do when mine are loose is to pinch them carefully with a pair of needle nose pliers on both curled sides so they pinch the male connector better. If the pinching description is not clear, do ask!

If the two ideas above reveal nothing, using an ohm meter you could check the resistance to see that there is no short circuit connect to the melted plastic wire. Again, if you get to this point, we can go through checking the resistance. It would be good if you can identify with a wiring diagram which ignition wire it is and post it marked on the wiring diagram.

69 OTS

And let me add… if it were my car, I would take out the ignition switch and clean the male connectors until they are very bright.

In addition, sometimes the rivet that hold the male connectors to the ignition switch assembly are slightly loose. This causes arcing and the male connectors get very hot. I had this problem and my ignition switch got very warm. My solution was, without undoing the rivet, to clean the rivet exposed parts and the male connecting parts to bright metal then solder them together. Sometimes hitting the rivet with a punch will do but for me solder is better.

And while I am at it, if I had the ignition switch out I would give it a good internal cleaning making sure all the contacts are polished nice and bright!!

69 OTS

Yeah not to say I’m telling you so BUT….
Your using a flamethrower 3 set up?
850 h/p ?
If your car is a true series 2 with the safety ignition CRAP switch
4 million volts going through that old junk isn’t going to hold up my friend
Peel back the banana,pull out everything ignition from the key to the dizzy
Or it’s only going to get worse
Send pics of the system your using
Good luck
Sorry my bad yours is 67
Yeah 4 million volts through THAT old crap won’t help either , I could only image what your amp gage is doing
Also what alt is in the car

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Double Ps You should be using a 3.0 ohm coil
The flamethrower 3 used for Camari hot rods is somewhere like .030

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In 20 odd years of using of my 3.8 I never had any problem whatsoever with the factory points ignition and distributor set-up. It never misfired and always had that beautiful 3.8 throttle response.

I don’t understand why anyone would change the factory set-up rather that doing or having done a proper tune-up.


My ameter gauge was normal, slight charge. The connecter coming out of switch is slightly loose. Does it make sense to get new switch and factory coil? Factory alternator.

Your all over the map with parts
List what’s in the car then go from
Old and new does not cut it
Matching everything in old posts is the only way
Either stay old school
Points or new all the wY

Original distributor
Original alternator
Petronix replaces points
Had original Lucas coil

Really sounds like someone needs a new mechanic or stop doing work themselves. You could have burned up your wiring harness. The lower the coil resistance, the higher the amperage going through the wires. Obviously, your car is not designed to handle that kind of load. If you have a spark problem, find out why. All you need is enough spark to ignite the mixture. More is just wasted. If you have a running problem, find out why. Petronix does make a high resistance coil but the Lucas Sports coil works really good with a stock system or even with the regular Petronix. Alternator has nothing to do with this problem. It would have melted down with just battery power. You mention the stock coil was not providing enough spark. What is that based on? How was it determined? Help is here if we know what the question is.


Yeah your mixing and matching……
Lucas Sport
Bosch blue coil
3.0 is a safe bet if you didn’t burn up the unit already
Again you also need to upgrade the plug wires as well
Ps what possessed you to put in that coil?
Dick , take over
Good luck hope it all works out

My Buddy is a mechanic, I was getting some hesitation when pushed.found a week spark and he ordered the coil to get a better spark. Car ran well until the smoke

Because the melt was at the connector on the ignition switch and nowhere else, my guess is that the ignition switch itself is the source of the heat. And that usually comes from contacts inside the switch having built up a resistance (current through resistance equals heat - at the resistance). The fact that you just changed coils is probably coincidental. This is a common problem on the SII ignition switch and is the cause of many of them burning up (mine smoked!). I only had to open the switch and clean and file the contacts.

Richard Liggitt


Thanks Richard, my car is a series 1, don’t know if the same problem. I may get a new switch. Ordered a Lucas Sports Coil just to on safe side.

I’d say the jury is still out on that. Knowing “Righty tighty, lefty loosey” doesn’t make one a mechanic. A good mechanic would understand that ignition is a system and would have been searching for the reason for a weak spark, and not willy-nilly swapping in parts that are wholly inappropriate for the system.

Listen to @Dick_Maury here.


Read the label on the box! It says “ultra-low 0.32 primary resistance”. That is about 10 times lower than it should be, so 10 times the current through the ignition switch (I know, not that simple, but close enough). Need to get a better mechanic…


Thanks everyone for your help

I had never heard of a coil that had resistance of .3 Ohms.

This means that with the ignition switch on, you had current of 40 amps going through you ignition switch instead of 4 amps for a regular 3 Ohm coil.

No wonder there was melting at the ignition switch!!

You have been lucky there is no more damage

69 OTS

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Dragsters with no alternator and things like that
Quick squirt then shut down

If it was my car, I would check the full path of the wire that had 40 ohms going through it to see if any other damage

69 OTS