MTFCA Forum

Hi everyone, I have a strange problem that I hope you could help with. I have noticed that at certain times, my coil box switch will zap me quite hard, so recently, I have decided to just kick the switch off, but now I have noticed when I was checking wire tightness while the car was running, I got zapped pretty bad by simply holding the non metal center of the spark plug wire. Are these things normal, and how would I go about repairing these problems? I was thinking something along the lines of a faulty ground?

It's pretty common to get a shock when touching the insulated portion of a plug wire, especially in warm weather when your hands may be moist.

If you're getting a shock from the primary side of the ignition system, that's not as common, but it can happen.

What are you driving? A wooden coil box would be more likely to give a shock than a metal one.

A friend of mine once had a 1950 Ford with a 6 volt electrical system. It had a large metal horn button in the center of the steering wheel. That thing would give you a strong shock when you honked the horn in the summer time, especially if you had your arm draped over the window sill.

You’re probably right, It has been very humid lately also, plus the coil box is original, so that could be the culprit. Thanks!

Skylar, a rebuild of your coil box is in your future! Plan on using the available thermoplastic version of the kit to all but eliminate any future rainy-day trouble. When it builds reliability (big time) into the car, I am a fan of modern materials and this is one of the few things I do to my cars that is less than Kosher (and has proven to be very wise if you get caught in terrible weather, since it is bad to drive in a driving rain, it is much worse to walk!)

Also check for a bare spot in the wires coming from your timer, Bob

The shock is most likely coming from a wood coil box with an internal short between the primary and secondary coil windings.

Is the ground ok?

Skyler Kimball wrote: ↑

Wed Jul 05, 2023 12:30 pm

Hi everyone, I have a strange problem that I hope you could help with. I have noticed that at certain times, my coil box switch will zap me quite hard, so recently, I have decided to just kick the switch off, but now I have noticed when I was checking wire tightness while the car was running, I got zapped pretty bad by simply holding the non metal center of the spark plug wire. Are these things normal, and how would I go about repairing these problems? I was thinking something along the lines of a faulty ground?

Two issues- It would help to understand what "coil box" you have. Wood or metal and even what style so a picture would help. I assume that the coil box is mounted to a wood firewall. So the Box is insulated from ground. To get a shock some wire , carbon track is making contact to the box which in turn is connected to the switch. Normally these are insulated. Now to get a shock with one hand on the switch another part of your body need so be grounded to the car - like holding onto the spider of your steering wheel. Is your switch one of the ones below. What condition is you box in?
-
Putting a grounded object anywhere near a spark is likely to spark Reason its high voltage

This problem is not caused by shorted coil windings!
I have investigated this problem several times and in each case it was a result of the coilbox having prevuiusly gotten wet, it was started ( a natural inclination of ther owner) and carbon tracks immediately developed in the wood back of the coilbox. Carbonized wood is electgrically conductive. Rebuild your coilbox with a non wood replacement material, you will correct the problem and it wont occur agian.
As I love ot say "trouble shoot and repair a wet Model T coilbox and it an experience you will not soo forget"
Ron Patterson

The coil box is a wooden unrestored original. It isn’t perfect, as a matter of fact, the battery post terminal didn’t even work at all last time I tried it. I used to run the car on battery, but got too lazy to charge up the lawnmower battery, plus the car runs not as well on battery, so I got a friend of mine to charge up the magnets, and I just start the car on mag only. No battery needed. May as well keep what I have… thanks for all your help!

Skyler Kimball wrote: ↑

Wed Jul 05, 2023 9:49 pm

The coil box is a wooden unrestored original. It isn’t perfect, as a matter of fact, the battery post terminal didn’t even work at all last time I tried it. I used to run the car on battery, but got too lazy to charge up the lawnmower battery, plus the car runs not as well on battery, so I got a friend of mine to charge up the magnets, and I just start the car on mag only. No battery needed. May as well keep what I have… thanks for all your help!

I hope all of this means that you'll rebuild your coilbox, as Ron (and others) suggested. Since you're somewhat new to the forum and may not "recognize" Ron, I'll tell you that he's a very seasoned "pro" at this. Rest assured, you've received some very good advice (from him and others here as well!).

Rebuilding the coil box on a T isn’t rocket science. Lots of information, pictures, and good advice about doing it is right here on the forum. Parts are plentiful and very reasonable.

It’s a good way about learning about 100:year old technology that worked before computers and digital media way of thinking!!

I will in the future, but for now, as long as it hasn’t been giving me any problems other that a zap here and there, it doesn't bother me too much. I have some other projects to work on that are a little higher on my list. I do need to install some front shackles, due to the old ones so worn, that they’re rubbing on the front axle. This car has a long laundry list, and the coil box was added to that list. Thanks for all your help and suggestions!