Electrical wizards, I need advice

[Robdogg67]

There's a Duraspark II ignition system in my 67 and I also replaced main front wire harness and all motor electrical wires. It has worked fine for 2 years but a couple weeks ago the car shut down while I was driving. I knew it was electrical and after a closer look I found some shoddy wiring and blown "Accessory" fuse under the dash from the knucklehead shop that did the wiring for me. They were running the ignition 12v off my radio lead and also spliced in a supply for electric choke on the same lead. I fixed the bare wires they left exposed and isolated the 12v ignition box supply to the stud behind the ignition switch and I'll plug the choke lead somewhere else. All engine & firewall grounds are good.

Now bare with me as I thought I had the problem solved but I actually found the real problem. I put a new fuse in the ACC (#1) location in the fuse box. I then turned the ignition to the On position and happened to have my hand behind the ign. switch to where the 3-4 wires come out from behind the switch. There are 2 large dia. wires back there, one is yellow and the other looks pink. The large pink wire was very hot which was probably the cause of blowing the acc fuse in the first place. I took the fuse out and turned the ignition back On and the pink lead is fine to the touch but of coarse I have no turn signals or back up light and radio supply until the issue is fixed and I can put the fuse back in.

The pink wire (from the ig. switch) disappears in the spider nest of wire behind the gauges and goes who knows where. Here's another clue, with the key "On" and the ACC fuse in (pink lead now getting hot), the voltage to the "I" terminal on the solenoid is only getting 5.5v. But when I take the Acc fuse out, the I terminal gets 12v.

Does anyone have any suggestions on what or where the problem might be? thanks in advance.

 

[69gmachine]

You have to start by getting a voltmeter and a wiring diagram for your car. Trace the power from the main feed going into the dash (black w/yellow stripe on a 69) to the ignition switch and then all the way out to the coil. It sounds like the resistor wire is shorting to something and pulling too much current. That's just my first swag though. Always be prepared to adjust your theory based on your findings.

After you get your basic tools and you've traced as far as you can go, come back with your progress report and we'll try to help you from there if you still need it.

 

[jikelly]

Yeah a voltmeter will help you hunt down the culprit. I also agree with the resister diagnosis, but the VOM will help you pinpoint the problem. A wiring diagram will let you find out where that pink wire goes.

 

[GNGREN]

The resistor wire will get warm even when there is no problem. Especially if you just turn the ignition to on and not start the car. Atleast mine is that way. Been doin it since I originally bought it back around 1990. Although I still have points in it, but when I upgrade to the electronic I know you usually need to get rid of the resistor wire anyway, to get full voltage to the coil.

 

[Robdogg67]

Today I inspect all wiring behind the dash and everything appears in order and loooks in great condition for 40 years old underdash wiring. I did notice that the Mustang Steve diagram for duraspark conversion has changed to eliminate the pink resistance wire but I did mine per his original one two years ago which kept it. I called MSD today to see if I should run the resistor wire whith the Dura II module, duraspark dizzy and MSD Blaster 2 coil - they said Yes.

GNGREN says it's normal for the resistor wire to get warm so now I'm totally confused as there is so much conflicting info about the resistor wire or not, warm pink wire normal, ect... Does anyone else know if their pink wire gets warm?

I'm now thinking that maybe I don't have a problem other than there may have been too much stuff (backup lights, turn signals, radio, electric choke and duraspark 12v power lead on that 14amp ACC fuse circuit. But why did it work fine for 2 years that way? I also pulled the fusebox and everthing look fine back there in terms of wire leads. I might pull the ign. switch tomorrow and make sure the connections are good.

I plan on just putting everything back tomorrow and separating the Duraspark 12v supply to the lug behind the ignition switch which should relieve some power off that ACC circiut unless someone gives me some other ideas.

 

[Capt Dan]

Sometimes fuses just blow. Maybe a bit closer to overload than designed for two years.

 

[65ShelbyClone]

If you're not adverse to having a GM component in your car, you could get rid of the Duraspark box and use a 4-pin HEI module instead. I would also recommend putting the ignition on either its original circuit instead of through the stereo or give it a new dedicated circuit.

 

[mustangmike6996]

i completely agree with running those wires off of a new circuit. you said yourself looks like shoddy wiring job, now is the time to repair that and make it the way it should be. as for the wire getting warm its most likely due to being a resistance wire, anything with resistance will produce heat. (example-light bulbs) also as said before fuses sometimes just blow, especially if there are more loads installed than what was engineered by the factory..either way let us know what you plan to do and post pics if you can.

 

[69gmachine]

Agree with the general consensus (and the wiring diagram) that the ignition circuit should not only be its own circuit, but it shouldn't have a fuse to blow in the first place.

I've been running Duraspark ignitions in early Mustangs since the 80s. I always cut the brown wire coming from the solenoid (under the dash somewhere) that is normally used to supply 12v only at engine start and instead, supply a constant 12 volts with a parallel wire to the resistor wire. That leaves a very stock appearance under the hood. There are several threads that cover the Duraspark conversion here on Stangnet.

The new MSD 6AL2 has a built in rev limiter and automatic retard on start up (like the Duraspark module) in addition to the multi-strike. Even though I've added a Soft Touch rev limiter to my Duraspark ignition, I really want to get one of these new ignitions to try it out someday.

 

[Robdogg67]

Just an update, I fixed all the shoddy underdash wiring and found an extra wire lead that I asked them to bring into the car for future tach but of course they just cut the end and that wire could have easily contacted metal under the dash shorting the system. After covering the exposed end, I also took the radio and electric choke off the ignition (ACC) circiut to minimize the load. It drove fine so far but we'll see after a few more cruises if it's fixed. I did keep checking the resistance wire and it felt warm and after hearing your responses, I'm convinced it's normal.

By the way Larry, I'm buying the new MSD6AL-2 this week ($240 after $25 MSD rebate through 8/31). I've planned on going MSD eventually but with the new 2-step rev limiter, no rev plugs model and my recent issue has made me get it now rather than later. I think it will get powered right off the battery which should simplify the wiring.

 

[69gmachine]

By the way Larry, I'm buying the new MSD6AL-2 this week ($240 after $25 MSD rebate through 8/31). I've planned on going MSD eventually but with the new 2-step rev limiter, no rev plugs model and my recent issue has made me get it now rather than later. I think it will get powered right off the battery which should simplify the wiring.

Cool!