Burnt Ignition Switch Resistor Wire

[jbanna]

A disaster just sidelined my ’78 7 miles after I solved the steering wheel and gear issue; now I’m forced to ask for help from you electrical forensic experts, and I’ll be thorough:

Last summer I had issues with my courtesy lamps and clock, which are on the same fuse, because one of my wires was pinched between the steering wheel and its mounting bracket, shorting out the fuse; eventually I found the problem and fixed it, along with installing my new quartz movement clock…all was well for several months, until I finally decided to start the steering gear project.  After completing that job, I went for a drive:

First, I had to charge the battery because it had been in use off and on for a couple of weeks, and the car wouldn’t start; however, after charging the battery I was able to start the car and test drive my alignment…all was right then except for a little off-center turn signal cam, meaning steering adjustments still need to be made; however, after 7 miles with no issues, I parked in a clinic and came out a few minutes later to a struggling starter, and then began to notice burnt plastic smoke coming from my vents.  I turned the ignition off, and removed the access panel for that spot – to my dismay, fire was already trying to burn up my car!  Fortunately I was able to blow out the fire before it really messed up the car, but unfortunately many wires are either burnt or melted – has anyone experienced such a problem? I’ve posted pics and did some general research – it seems problem wire was the brown and white resistance wire to the ignition switch, but why did it just now fail so badly?  I’ve seen suggestions that the alternator could have done it, but it’s less than a year old and seemed to be working perfectly, although I did just notice the alternator post is loose and wiggles a bit; I also replaced the starter 3 months ago to address intermittent slow cranking, but the new starter wasn’t much better, so I upgraded the battery cables to 2 gauge, which didn’t help either. The wires on the engine compartment side appear undamaged.

So, 1) Is the burnt wire the ignition switch resistor, and if so can a replacement be sourced; 2) If I have to make one myself, what are the resistor specs (the length of the wire and the coil should be a certain ohm rating); 3) The wire is stainless steel and can’t be soldered, so how does one efficiently connect a new wire to the connectors at each end; 4) Causation – alternator vs starter…I’m virtually certain no wires were damaged before the problem occurred as I checked them all last summer when I resolved my courtesy lamp circuit short; 5) Whether or not the starter caused the problem, any recommendations on a quality mini starter for a Pontiac 455 with headers; 6) and finally, how much of the wiring must be reinstalled to get my windows down?

I have so much experience with this car, but new mysteries keep happening…thanks for any help!

[5th T/A]

I feel for you, after all the steering gearbox issues you can't catch a break.

A brief explanation on your cars electrical system wiring. There is a heavy gauge wire from the positive battery terminal directly to the starter. It is not fused. There is also a smaller, probably 10 gauge wire from the positive battery terminal to the back of the alternator. This is the large stud on the back of the alternator and the path that charges the battery. That same terminal is connected to a fusible link that runs on top of the driver's side rocker arm cover and goes down to the firewall wire harness bulkhead to the fuse block inside the car. This is the source of power for everything in the car with exception of the starter motor armature, but not the solenoid. Any major short should cause the fusible link to melt in two just like a fuse. Think of the fusible link as the same as the main circuit breaker for your house electrical panel. Power from the terminal block runs directly to the ignition switch, this circuit is not fused other than from the fusible link. From the ignition switch a smaller wire goes back to the terminal block, out through the firewall and back to the starter solenoid. When you turn the key to the start position it will send 12 volts to the solenoid to energize the starter. If the solenoid is drawing too much current it should cause the fusible link to open and protect the cars electrical system.

Do you have a real fusible link there or did someone replace the link with a piece of wire. Or maybe replaced the link with a higher current rating fusible link that failed to act as a fuse. If I remember right, the link is not soldered but is crimped to a regular wire close to the alternator end.

I don't believe the alternator is the cause. If it was the 10 gauge wire running between the alternator and positive battery cable would have melted. I think most likely the starter solenoid has gone bad, drawing too much current. I am sure fusible link is available, but you have to make sure you have the proper rating. The under dash burnt wires can be repaired or you can buy a new harness. For that matter you can buy a new engine wire harness that will have the correct rating fusible link in it.

[jbanna]

More info:  I have discovered the burnt BrW wire is the exciter wire running from the ignition switch to the alternator, and the wires from the bulkhead connector to the alternator were undamaged; however, the plastic bushing on the "new" alternator is cracked and the post is loose, with obvious evidence it burnt, probably because the looseness allowed an internal short, which travelled back to my ignition switch when I was trying to start the engine, frying the smaller gauge exciter wire; however, I still don't know why GM used a single strand stainless steel wire for the exciter circuit, which I am now trying to source...any more insights?  I'm wondering if I can substitute a copper wire for the 24 gauge stainless steel one?

Also, new pics are attached - the "resistor" I imagined was just a wire nut I put on that wire when I cut it probably 30 years ago for re-routing, and forgot about...I really want to make sure I don't put everything back together with new parts and have the same thing happen again - I know the car is 46 years old, but it has been really well-maintained, garaged, and driven the whole time, for over 350k miles, so no rodent damage!

[5th T/A]

If the alternator has shorted the exciter wire, then you should probably see 0 ohms resistance from that terminal to the alternator case ground. Unless it burned completely open inside the alternator. Do you have an automotive electric shop near you where you can have them bench test the starter and alternator? Maybe discuss your problem?

[jbanna]

The alternator was bad, and I'm going to replace the starter with one of the high torque models; however, now I have to find some replacement stainless steel wire with insulation, or perhaps I'll have to wrap new wire with some sort of tape and heat-shrink tubing and then get it into the connectors at each end...what a nightmare this has been!