Smoke from ignition switch?

[JJorgensen52]

This is just a curiosity question. On both of my trucks, once in my time of ownership (as it happens, both within a few weeks of their respective purchases), I had the ignition in the on position but not running, and smoke / faint burning electric odor started coming from the ignition switch under the dash.

Both trucks, happened only once. Turned off, left to sit, has been fine since.

Is this some artifact of sitting for a long time, moisture in the switch, or should I be expecting my trucks to burst into flames?

[VetteVet]

Turning the ignition switch on and leaving it on provides a path to ground if the points are closed. The current flows through the coil and to the points to ground. The resistance of the coil causes a heat build up in the ignition wire (pink) at the key switch and in the coil windings. this circuit is not fused so an overcurrent condition may exist which acts as a short to ground. Generally the coil windings will burn up before the ignition wire does.

During normal operation the current through the coil is dissipated when the coil discharges to fire the plug so it won't buildup enough heat to burn up the windings or the ignition wire. This is further prevented by using the resistance wire in the ignition circuit to the coil to reduce voltage to the coil during normal running.

The smell is the plastic insulation on the wiring overheating.

[WIDESIDE72]

A lot of people are not privy to the fact that you shouldn't leavethe key in the "on" position with the vehicle not running if equipped with a points ignition. My first car back in the 80's was a 71 El Camino with points. I changed it to HEI soon after I started driving it daily. I'm not surehow I learned. I think my dad told me it wod burn up the points. We are all spoils today with electronic ignitions. Btw, new cars not even let you try to crank an ready running engine!
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[Square_78]

Even now I can't bring myself to even leave a new vehicle in the "on" position without the engine running. It's just force of habit.
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[Ol Blue K20]

This is why we have the accessory position
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[LockDoc]

Originally Posted by Ol Blue K20

This is why we have the accessory position
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Just for the record, the '67's, and some early '68's, do not have an accessory position on the ignition switch. (if they still have the original switch in them)

LockDoc

[Ol Blue K20]

Originally Posted by LockDoc

Just for the record, the '67's, and some early '68's, do not have an accessory position on the ignition switch. (if they still have the original switch in them)

LockDoc

Ya know LockDoc thats the beauty of this site, I just learned something new again. I wonder if it was because trucks were work vehicles and you didn't listen to the radio with it not running. Thanks for the info

[JJorgensen52]

The '69 has an HEI in it, has the entire time I've owned it.

I did not know this about points - learn something new every day!

And for the record, I don't normally leave the key in the on position, only when chasing electric gremlins that require it