1960s melted solenoid to coil wire

[David Greenburg]

Went to start my '60 today. Cranked okay, but didn't fire, and then I got smoke from under the hood. Never a good sign. Turned out that a section of the insulation on the yellow lead  from the starter solenoid to the coil was melted off, exposing a stretch of bare wire. I must admit that this wire previously looked a bit stiff and tired, although I saw no obvious breaks in the insulation. And prior to trying to start the car, I had been poking around in that neighborhood checking the valve cover bolts. I'm obviously going to replace the wire. But I'm wondering if the cause was simply a brittle old wire that shorted against something, or whether it's more likely that there's an issue with the solenoid that caused it to cook the wire, and replacing it will just cause a repeat. 

[Cadman-iac]

  David,

 I wouldn't suspect your solenoid as it's just an on/off switch basically for that wire to the coil, and it only energizes when the starter is engaged.

 I would just replace the wire and carefully inspect the others running alongside it for damage.

 Age alone is reason enough to consider replacing the harness, at least the under-hood one, as it's also subjected to the heat of the engine.

 If your harness is otherwise in working condition, you can use it as a template to make a new one if you're able to do that kind of work.
 Most all of the terminal ends are the Packard series 56 and still available from several sources. The plastic connector housings can be reused unless damaged.


 Rick

[The Tassie Devil(le)]

All that wire does is to supply 12 volts to the coil to assist in starting.  There is the "resistered" voltage still there at the coil.

When the Starter Motor is cranking, with a poor battery, there can be a voltage drop to well below 12 volts.   I have seen drops as low as to 8 volts.   If this happens, then the actual Ignition wire through the Resistor to the Coil will drop even below 6 volts, which makes the low voltage Coil hard to operate.   Hence the direct voltage whilst cranking via the Solenoid.

If the wire is actually shorted out, then that is a problem.

Bruce.

[David Greenburg]

This afternoon I looked more closely at the wiring. It's definitely time for a new engine harness. I temporarily spliced in a new segment of wire in hopes of confirming that this was the culprit and that everything else is okay. For about a 5 inch segment near the coil, the wire was bare; the insulation was completely gone. I'm guessing that it was shorting against part of the carb linkage. Now when I try and start it, the car cranks fine and there's no smoke, but the car won't start. I'm wondering if the short cooked something else, like the coil. 

[Big Fins]

Possibly the resistance wire has a break in it, burned points, condenser, even the coil may be shorted.

This is when having a Sun Analyzer is a great thing.

[James Landi]

David, how "handy" are you with a multimeter?  Checking voltage at the coil with the ignition on, (with one probe to ground) should yield around 8  volts.  If not, check the ballast resistor for voltage with the ignition switch on... if one side has 12 v and the other side has nothing, the ballast resistor blew out when the yellow wire was shorted and your car won't start.  To check the solenoid yellow wire boost, check the voltage at the yellow wire connection while cranking... you should see the voltage "jump up" to between 11.5 and 12 volts while cranking.  If there's no increase while cranking, then the yellow wire from the  solenoid is not working, and the solenoid may be compromised because of the short.

[Roger Zimmermann]

James, are you sure about the test? With key on, the voltage should be 8 to 9V. If the other side has nothing, it casn be because the point are closed.
Only by atuating the starter motor, the voltage at the coil should be near 12V.
Or am I wrong?

[David Greenburg]

I'm pretty good with using a VM once I know what I'm testing for. I can also switch out parts like the coil from my '61 to try and isolate the problem.

[James Landi]

Roger writes:"James, are you sure about the test? With key on, the voltage should be 8 to 9V. If the other side has nothing, it casn be because the point are closed."
DAVID: Don't switch out the coil and points and condenser.  Your shorted yellow will not affect those parts unless they failed by coincidence (Heinsenburg's "Theory of Uncertainty" in play!)
With the meter connected on the yellow wire and the ballast resistor side of the coil and the other side of the meter CONNECTED To GROUND, David should have around 8 or nine volts even if his points are open.  With the points closed, he still should have battery voltage LESS the resistor because the key supplies that ignition current with the turn of the key at all times.  When David is cranking, his yellow wire is connected to the starter solenoid, and the starter's plus side to the battery provides the boost power to the coil as long as David is cranking the starter, when the engine starts, the yellow wire disconnects from the soleniod, thus the coil runs on the ballast's dropped voltage during the normal run (not start mode).

[David Greenburg]

Doing the aforementioned voltage test at the coil, I'm getting nothing-no movement of the meter needle at all with ignition on or when cranking. So now I'm thinking the resistor wire is bad. It's adjacent/bundled with the yellow solenoid wire, so perhaps it got cooked when the short occurred. The FSM gives a spec for the resistor wire, so it looks like I can test the resistor wire if I can rig up leads to reach the ignition switch connector after doing one of my favorite jobs on these cars- opening up the dash (sarcasm alert), although I'll have to do that anyway to put in the new ignition harness.

[James Landi]

 I suggest that you try connecting a wire from the battery plus side to the coil (yellow/ballast wire) to make certain the car starts and runs for a few moments.  Hard to fathom that you've no current from the solenoid and the ignition switch unless that short burned out the ballast wire and/or ignition switch and the solenoid too.  Yikes!  Don't hesitate to connect with me.  If you wish, we can talk on the phone...   James

[David Greenburg]

Thanks, James. I'll DM you a bit later.

[David Greenburg]

I hate an unfinished story, so to close the loop on this one, the issue turned out to be a short in the a/c cutout switch, which had been wired to the hot side of the coil (not by me) when the a/c was converted from an A5 to an A6. Many thanks to James for guidance in tracking down the issue and preventing me from needlessly replacing parts.