Topic: Coil failure

[ruppstang]

I have been having trouble with hot starts on our unrestored 68 High Country Special. I had thought it was a fuel issue because at first it only happened on long trip in hot weather. But since it has happened more frequently I began to think it was something else. Today I thought I would check the coil and sure enough it was well on it's way to failure. I have had this problem when using Pertronix on a stock coil before but not with points. 

[markb0729]

Yup, looks like it's leaking.  Did you happen to check the resistance when it was cold and hot?  Just curious.

[midlife]

That's terrible: things don't last as long as they used to.  Who'd expect only 50 years of utility and use before it broke? 

[ruppstang]

Yup, looks like it's leaking.  Did you happen to check the resistance when it was cold and hot?  Just curious.

No I did not, I should have but when I saw how much it was leaking I just replaced it.

It turns out it was not the problem of the hot starts. I went for a longer drive and still had the hot starting problem. Still could be the condenser or a fuel problem.   

[RoyceP]

The coil would not know the difference between a Pertronix unit and points if the Pertronix unit is wired per their instructions. Coils will fail if they get a full 12 volts / the resistance wire has been removed.

No I did not, I should have but when I saw how much it was leaking I just replaced it.

It turns out it was not the problem of the hot starts. I went for a longer drive and still had the hot starting problem. Still could be the condenser or a fuel problem.

[ruppstang]

The coil would not know the difference between a Pertronix unit and points if the Pertronix unit is wired per their instructions. Coils will fail if they get a full 12 volts / the resistance wire has been removed.

Yes you are right. It must have just been another old coils time. I think if I remember correctly the Pertonix does not work as efficiently through the ballast resistor and the lower voltage.

[RoyceP]

The Pertronix unit gets a full 12 volts to its red wire if connected in accordance with the Pertronix instructions. The coil must receive its current through the resistance wire.

[jwc66k]

The Pertronix unit gets a full 12 volts to its red wire if connected in accordance with the Pertronix instructions. The coil must receive its current through the resistance wire.

I think that may be a Pertronix pitch to get you to buy one of their coils. My Pertronix Type I has got at least 10 years on it in a 66 "A" code Hardtop and works fine with the regular coil and resistance wire.
Jim

[ruppstang]

As I recall the Pertronix instruction saying to wire around the ballast resistor and use their coil. I have to check if I still have one around.

BTW I also used the Pertonix powered by a Autolite coil and the ballast resistor for many years.

[carlite65]

I think that may be a Pertronix pitch to get you to buy one of their coils. My Pertronix Type I has got at least 10 years on it in a 66 "A" code Hardtop and works fine with the regular coil and resistance wire.
Jim

same here. no problems in almost 20+ years with one.

[RoyceP]

I installed a Pertronix in 1990 on what used to be my daily driver Ranchero with its 289-4V auto. 30 years and more than 100,000 miles later it is still working with that old original Autolite coil. In this case it was wired the way the Pertronix instructions said back then, which has the red Pertronix wire connected to the + side of the coil and the black Pertronix wire on the - side of the coil. So the resistance wiring, and all other wiring under the hood is untouched.

I think that may be a Pertronix pitch to get you to buy one of their coils. My Pertronix Type I has got at least 10 years on it in a 66 "A" code Hardtop and works fine with the regular coil and resistance wire.
Jim

[jwc66k]

So the resistance wiring, and all other wiring under the hood is untouched.

I don't think that Ford expected many failures of the resistance wire as it is permanently bonded to the connector. If it was subjected to failure, there would have been a short lead with a single bullet type connector to mate with another bullet type connector that was part of the resistance wire. I've seen only one Mustang with an external resistor mounted on the firewall, obviously to replace a bad resistance wire. A replacement wire is sold by Mustang (and others) vendors, so maybe it does fail.
I'm keeping my fingers crossed.
Jim

[preaction]

The one thing with a Petronix is if you are troubleshooting and leave the key on and not running the coil will get hot enough to boil water.

[Bob Gaines]

The one thing with a Petronix is if you are troubleshooting and leave the key on and not running the coil will get hot enough to boil water.

Same thing when you hot wire a vintage Mustang . The full 12V causes the coil to overheat. I heard of one even blowing up because of it got so hot.

[RoyceP]

I have owned a few 67 - 68 Mustangs and Cougars that had resistance wires which were still operating but absolutely charred from too much current. These cars all had aftermarket Mallory coils, the big rectangular ones that were so popular in the days before MSD. Some of my friends also used the gigantic Accel coils. There were other brands back then too. Any of these aftermarket coils have a lower resistance than a stock yellow top coil, which increases current in the resistance wire because it is in series with the coil. The proper way to use one would be to bypass the resistance wire and of course any factory tach, and use a ceramic resistor that could take the higher current without melting.

Of course back then we were all bulletproof and invisible and knew more than the instructions in the box.

I don't think that Ford expected many failures of the resistance wire as it is permanently bonded to the connector. If it was subjected to failure, there would have been a short lead with a single bullet type connector to mate with another bullet type connector that was part of the resistance wire. I've seen only one Mustang with an external resistor mounted on the firewall, obviously to replace a bad resistance wire. A replacement wire is sold by Mustang (and others) vendors, so maybe it does fail.
I'm keeping my fingers crossed.
Jim