This adventure started out of the blue when I went to start the 65 and nothing happened except the ammeter gauge would peg at -40 as soon as I turned the key to the on position - with no change when it went to the start position. So no starter motor engagement or solenoid click. I replaced the battery, and then the starter and solenoid with no change.
The meltdown occurred when I was checking the voltage to the solenoid while the key was being turned to the start position. With my volt meter on the S terminal of the solenoid, and grounded to the starter bolt my wonderful wife turned the key to the start position. For the first time the new starter engaged. Because I was not expecting the starter to engage I flinched, removing the voltmeter wire from the S terminal. The starter stopped, but the garage was filling with smoke. I lowered the lift - which seemed to take forever - and flipped the battery shut off switch which stopped the carnage.
None of this makes any sense to me. I'm hoping the issue was with the old - it was a replacement - ignition switch. Here's the NOS ignition switch that I picked up off of Ebay.
I just replaced the under hood harness with a new lectric limited harness after this happened.
I just got the under dash harness out. I opened up the harness and traced the smoked ballast resistor wire back to the ignition switch. I could not find any other damaged wires in the harness. The plug on the wire going into the ignition switch is melted as well.




I may never know why that wire smoked, but since the only wire that smoked went directly from the ballast resistor to the ignition switch, I'm thinking the old switch was the problem. But electrical diagnosis is far and away my weak point while working on cars.
Smoking the new harness would probably result in a few new cuss words being created on the fly as well as a few blood vessels bursting in my forehead.
So - anyone have any suggestions on how to proceed carefully?

 

One reason why you should use a fusible link at the starter. Worth it to save your wiring. Also, I did add an inline fuse on the ammeter gauge and ignition switch. GM was never good about adding these things to the engine harnesses back in the day.

 

The current went through the switch no doubt destroying it but what you want to look for is the burned wire and/or component farthest away (in circuit terms) from the battery and then through the switch. The burned out switch is a symptom but not the cause.

As best I can tell you are showing a black wire with a pink trace and that goes from the solenoid 'R' terminal to the coil and resistor. If it was connected and burned like that, the coil is likely dead shorted. If it was not connected to the solenoid then the other end must have been connected to the resistor and the end near the starter must have been grounded. The problem with that is that in that case the resistor should have gotten very hot but not much more UNLESS that wire and the 'R' circuit were connected on the wrong side of the resistor. In that case, the the Black/pink wire were grounded then you would get a huge short through the ignition switch and lead to pretty much what you observed. It's even possible that the ignition switch contacts welded themselves.

P.S. This is a very good reason to make sure that there is either a fusible link or an auto-reset circuit breaker in the main feed because otherwise the ignition circuit is completely unprotected including the solenoid 'S' circuit which energizes the pull-in and hold-in coils. I actually prefer the breaker to a fusible link (never a fuse; they are too fast) because I have visions of that fusible link blowing while a locomotive is 50 yards away.

 

Thanks for the replies.
I will install a fusible link between the S terminal on the solenoid and the harness.
The smoked wire I'm showing is the black/pink ballast resistor wire that runs from the ignition switch to the ballast resistor. I just replaced the under hood harness. That harness was a replacement M&H harness and still looked in great shape. So just the wire from the ignition switch to the ballast resistor is burned.

 

I would be suspicious of the pink wire either shorted at the ignition shielding or you shorted it enough with the meter lead? Many have melted wires by touching the distributor shielding to the pink wire from the ballast.

 

I think you will.
It is common for the ignition shielding to be installed pinching the coil primary wire and if that is your case as I suspect you would discover the problem immediately upon switching ignition on. Look for the burn mark on the bottom edge of the shielding. This has been much discussed & and experienced, unfortunately here over the years.

Dan

 

I did just replace my spark plug wires a couple of weeks before this happened, and it's entirely possible I pinched that resistor wire. I don't see any burn marks on the ignition shielding, but that sure could be the cause.
Since I just replaced my starter, I put the car up and double checked my wiring to the solenoid, and it is correct - black and pink on the R terminal. I did just replace that under hood harness after this happened, but I'm sure I had the other harness wired correctly as well.
I'm still so confused as to why when I was checking to see what was happening when the ammeter was pegging negative that the starter only engaged when the wife turned the key to start and I had the volt meter on the solenoid S terminal and the starter ground bolt - and stopped when I jolted away - but then the wire continued to burn until the battery was disconnected. I might never know why that happened either.
I appreciate everyone's input.

 

There you go. You likely pinched the pink wire initially not enough to ground it but eventual vibration cut through it. This problem is common, long discussed here with solutions offered, including using door edge guards on the bottom of the shields Best way is to be careful.

Dan


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My solution is leave that damn wire cutter off. It serves no purpose (unless you're still listening to AM radio) and only causes heartache. By leaving it off you, also, allow more air flow to the ignition coil to keep it cooler. JMHO

 

You have to careful putting in on and off, watch the pink wire is not getting caught and keep the coil wiring parallel to the firewall and your good, most of the time.

 

I also was concerned with the pink wire and shielding problem. The pink wire seemed extra long, and I wondered why. The AIM is useless, it doesn't show the routing. After trying various routing attempts, and not wanting the buba solutionI, I think I found the solution. It was to simply take the pink wire, feed it under the tack cable and then to the coil.

With routing the pink wire under the tack cable its highly unlikely to contact the shielding. I would recommend this solution to all.