Need Some Help Replacing Coil Wiring

[Floyd B.]

At some point in the past a previous owner(s) of my '69 L36 replaced the white coil resistance wire from the coil to the fuse block with a non-resistant wire, then added a C2 style external ceramic resistor. I want to get the wiring back to something that resembles the original configuration. To do this, I need to replace the white resistance wire.

What type of wire should I use for this and where can I get it? Or is my only option to construct a wire with a small inline resistor?

Thanx

-Floyd-

[Brad H.]

Re: Need Some Help Replacing Coil Wiring

Floyd,
The 69 uses a fiber jacket yellow wire with, I believe, a blue or purple spiral striped resistance wire. The wire is available from Lectric Limited. I would imagine they would sell you just this section of wire. The only other option I know of will be to run a switched hot wire to a ceramic resistor block similar to the 67. Resistors are available at all the standard Corvette retailers. You should also have a wire coming from the starter solenoid up to the pos side of the coil as well as the resistor wire. This wire goes hot at ignition switch activation by utilizing full 12 volts off the starter relay/starter. This full 12 volts is powered only when the switch is in start. When released, this wire is depowered. This additional voltage at start was to push points voltage to 12v rather than roughly 6v normal operating voltage. This extra electrical jump was an aid to starting and as soon as the switch was released, power was killed from the starter/battery to help retain the longevity of the points.
if you have any more questions, I'll do my best to help if I can. Some of the wiring can be pretty confusing.
Brad

[Mark E.]

Re: Need Some Help Replacing Coil Wiring

Is the rest of the engine harness perfect? If not, this may be a good opportunity to remove it and have it repaired. R&R is straight forward and at least one of the harness vendors used to do repair/restoration of existing harnesses. This involves replacing any damaged wires and connectors for much less $ than a new harness.

[Floyd B.]

Re: Need Some Help Replacing Coil Wiring

Brad and Mark,

Thanx. Contacting LL for a section of wire is a good idea. The car is currently a driver and the wiring is in overall pretty good condition for a 47 year old car. At this point the car is a driver and a future frame-off restoration project. Even though I plan on a full restoration and replacement of the wiring harnesses down the road I hate having things "wrong" in my car (OCD). I have corrected several electrical alterations made by previous owners and now want to get the coil set-up back to something similar to "original." That's why I resist using a C2 style external resistor block.

It looks like one of the early owners removed the resistor wire to be compatible with a high performance coil that didn't need it. Sometime after that someone decided to go back to a stock coil so they installed an external resistor block and mounted it on the firewall with a drywall screw.
I now want to install a U505 AC Delco coil with a new resistor wire. My other (and easier) option is to use an E552 coil and leave the wiring as-is.

-Floyd-

[Mark E.]

Re: Need Some Help Replacing Coil Wiring

Sounds like a plan.

I recently ordered the U505 and was disappointed. It looked significantly different than the original and was oil filled (originals are epoxy filled). I probably could have wiped off the Made in China markings and considered keeping it if the oil didn't slosh around so much (that didn't seem right).

I just ordered a E552C and hope it's a better match.

[Floyd B.]

Re: Need Some Help Replacing Coil Wiring

Thanx Mark,

Please let me know how the E552C works out. If it meets your expectations then I'll probably do the same and go with the option that doesn't require replacing the resistor wire. In the meantime I just sent an email to one of the wiring harness vendors and asked if they would be willing to sell me the resistor wire alone.

[Joe L.]

Re: Need Some Help Replacing Coil Wiring

Brad and Mark,

Thanx. Contacting LL for a section of wire is a good idea. The car is currently a driver and the wiring is in overall pretty good condition for a 47 year old car. At this point the car is a driver and a future frame-off restoration project. Even though I plan on a full restoration and replacement of the wiring harnesses down the road I hate having things "wrong" in my car (OCD). I have corrected several electrical alterations made by previous owners and now want to get the coil set-up back to something similar to "original." That's why I resist using a C2 style external resistor block.

It looks like one of the early owners removed the resistor wire to be compatible with a high performance coil that didn't need it. Sometime after that someone decided to go back to a stock coil so they installed an external resistor block and mounted it on the firewall with a drywall screw.
I now want to install a U505 AC Delco coil with a new resistor wire. My other (and easier) option is to use an E552 coil and leave the wiring as-is.

-Floyd-

Floyd------


I think that either the U505 or E552 will require the resistance wire.

[Mark E.]

Re: Need Some Help Replacing Coil Wiring

Floyd------


I think that either the U505 or E552 will require the resistance wire.

As OEM replacements, I believe that's correct. The wiring on these cars is designed to provide less than 12v to the coil in run mode using a ballast. This allows a separate circuit to supply a full 12v while cranking for easier starting. So always use a coil designed for a ballast resistor.

[Jim T.]

Re: Need Some Help Replacing Coil Wiring

Floyd, Back in the mid 70's something happened to the resistor wire going to the coil in my 1968 Corvette. I went to a salvage/junk yard and removed a nice looking resistance wire from another GM car. Carefully removed the electrical tape from the wiring of the donor car to remove it's resistor wire. The replaced resistance wire is still in use today.

[Mark E.]

Re: Need Some Help Replacing Coil Wiring

It may be harder to find vintage bits and pieces like that in a modern junkyard.

[Floyd B.]

Re: Need Some Help Replacing Coil Wiring

The problem I have is that it appears the wiring has been altered for installation of a high performance (e.g. Pertronix) coil. I think this leaves me with 3 choices:

1) Fix the wiring harness and replace the resistance wire. I wanted to do this until I looked at what this job would take. It would be a real PITA b/c the harness wiring is now wrapped in miles and miles of that heavy black cloth adhesive tape that has been baked for 20 years by the heat of the engine. Following the path of the coil wires to verify their end-points isn't all that straight forward b/c bubba the mechanic could have spiced the wires and I have already corrected several incorrect modifications at the fuse block in this car (i.e. wires terminating at the fuse block in the wrong location). I would rather avoid this job now and save it for the body-off resto about 5 years from now.
2) Put the external ceramic ballast resister back in (I think I may even have kept that drywall screw ). This is my least favorite choice b/c it's just wrong. I know that sounds ridiculous since the wiring harness has already been run through a shredder. But still...
3) Use a coil designed run "hot" with a full 12V at all times. Again, not correct to the car and I worry that I won't have other ignition components (points, rotor, condenser, wires, etc.) that aren't designed to work with such a coil.

I'm wondering if I have a fourth choice; Is there an AC Delco replacement coil that is designed to run w/o an external ballast resistor?

Thanx

[Terry B.]

Re: Need Some Help Replacing Coil Wiring

Hi Floyd

I had the same situation on my '68 L-36 with the ballast resistor and missing the resistance wire. I guess that was the practice during that time. There were more wiring problems with the car in addition to this one but that is another story. What I decided to do was to clean up the patched and spliced wiring mess the previous owner(s) had done and be sure that all the wiring was correct and safe. I purchased the wiring harness from Lectric Limited and everything went fine and I do not have to worry about spliced wires and shorts. Yes, it is a little more work and money but sounds like you are planning to do it eventually so you might want to consider doing it now and have the peace of mind knowing the wiring system is safe and the way it was originally designed. Good luck with your decision and outcome.

[Mark E.]

Re: Need Some Help Replacing Coil Wiring

I'm with Terry. Just remove the harness and send it to a vendor for inspection and repair. R&R is fairly simple, you'll eliminate possible electrical and safety issues with the suspect wiring, and the harness will be ready for your future restoration. Meanwhile your car will run properly.

[Floyd B.]

Re: Need Some Help Replacing Coil Wiring

...What I decided to do was to clean up the patched and spliced wiring mess the previous owner(s) had done and be sure that all the wiring was correct and safe. I purchased the wiring harness from Lectric Limited ...

Terry,

That's the same conclusion I have come to. After looking at my current harness and the effort it would take to repair, it is quite apparent that it will be MUCH easier to simply replace it. Like yours, my harness has several other problems created by previous owners. I also have an aversion to using old electrical or fuel system components - that seems like I would be begging for trouble.

My plan is to "suggest" to my wife over dinner tonight that a new wiring harness would make a wonderful Valentine's Day gift.

Thanx for everyone's input.

-Floyd-

[Douglas L.]

Re: Need Some Help Replacing Coil Wiring

That's the same conclusion I have come to. After looking at my current harness and the effort it would take to repair, it is quite apparent that it will be MUCH easier to simply replace it. Like yours, my harness has several other problems created by previous owners. I also have an aversion to using old electrical or fuel system components - that seems like I would be begging for trouble.

My plan is to "suggest" to my wife over dinner tonight that a new wiring harness would make a wonderful Valentine's Day gift.

I think you made the right choice. Just a bit of advise, if you have any inoperative fiber optics now is the time to replace the forward lighting harness while you're in there. Its a bit more involved than changing the engine harness but you'll be rewarded with brighter headlamps and fully functional fiber optics. Replaced both harnesses on my 68 L-36 with Lectric Limited parts and was extremely impressed with both the fit and quality.