1950s 1956 Ignition switch smoking

[56Fleetwood]

Problem with my ignition switch; started the engine with no problem but then got smoke coming from the ignition switch with a simultaneous grinding noise from under the hood. I shut it off immediately but still got smoke from ignition switch (disconnected battery immediately).

Where do I start diagnosing this problem?

[TJ Hopland]

I'm gonna guess that something failed in the switch leaving the starter engaged.  Failure could have been a simple mechanical failure where a contact came loose and stayed making contact for the starting circuit. 

I wonder if the starter actually stayed engaged like literally now being spun by engine thus making it into a generator (with no regulation)?   Or did it momentary drop out before the switch failed so it did disengage from the engine but then got re energized and was just grinding? At that point its not a generator so was the smoke just from how or where the switch failed perhaps shorting something to the body which I assume is metal and bolted into a metal dash so grounded? 

I don't know a 56 but I would say start with getting the the switch out so you can get a look at it.  I don't know if this means the whole lock and all or if just the electrical section comes off.  Seeing what the damage is and maybe using an ohm meter to see what pin(s) were involved may give you some clues as to what other parts of the system need to be investigated.

If it was mine I think I would want to get a look at the starter and ring gear too.  Not sure if there is an inspection cover or if you would have to pull the starter.  Verify that that was where the noise was coming from (should be obvious) and how bad the damage is.   If nothing looks like it was rubbing there then guess you have to take the belts off and spin things by hand to see what failed like maybe the generator?  Some odd failure that sent electrical spikes and cooked the switch? 

[56Fleetwood]

Thanks for this TJ. I'm hoping your suggestion of mechanical failure of the switch is correct. First things first, I'll remove the switch and test it.

The shop manual doesn't have any description of switch removal from what I can see. I assume the chrome bezel comes off first, so does the ignition switch just loosen up for removal after that?

Mike

[J. Gomez]

Problem with my ignition switch; started the engine with no problem but then got smoke coming from the ignition switch with a simultaneous grinding noise from under the hood. I shut it off immediately but still got smoke from ignition switch (disconnected battery immediately).

Where do I start diagnosing this problem?

MB,

Assuming the smoke came from a wire(s) insulator at the Ign. switch best option is to find out which one.
The Ign. switch feeds several others when it is moved to start the engine (SOL purple wire to the neutral switch) and released after (IGN pink wire to several fuses and other location) position.

If it happens during cranking I would start with inspecting and disconnecting the purple wire and checking for short.

If it happens after the engine started I would start with the pink wire and check for shorts by removing fuses (one at a time) and tracing other path that feeds from the same source.

Good luck..! 

[J. Gomez]

Thanks for this TJ. I'm hoping your suggestion of mechanical failure of the switch is correct. First things first, I'll remove the switch and test it.

The shop manual doesn't have any description of switch removal from what I can see. I assume the chrome bezel comes off first, so does the ignition switch just loosen up for removal after that?

Mike

MB,

Yes, you just need to unscrew the front bezel to remove the switch. If you do not have the tool you can use a needle nose BUT it is a PITA and you will scratch it, just be prepared.

[56Fleetwood]

Thanks. Will do as suggested and report back with my findings

[56Fleetwood]

Was able to get the ignition switch apart from the bezel. Examined the wiring and found the pink IGN wire has insulation scorched and melted (see pic). I'll probably repair this with a Permatex liquid electrical tape product as I can't reach it with heat shrink tubing.

Hoping this is the only cause of the smoking etc. Any comments/suggestions appreciated.

[TJ Hopland]

Did it look like that area was rubbing on something?  or just touching another wire that got even hotter and melted into that one?  You normally don't see a wire fail midway. 

[J. Gomez]

MB,

It is possible the wire insulation was crack exposing the wires to a ground source in the area, there are several cables (vent, etc.) that are close to the ignition switch hardness that may had rubbed in the open insulation causing the short. 

There is a possibility the expose wire was compromised with the short so you may need to splice the area. Remember that is the main +12V power feed to several sources (from the IGN switch) and the OEM wire is/was very limited handling the load.

Good luck..!   

[Lexi]

Was able to get the ignition switch apart from the bezel. Examined the wiring and found the pink IGN wire has insulation scorched and melted (see pic). I'll probably repair this with a Permatex liquid electrical tape product as I can't reach it with heat shrink tubing.

Hoping this is the only cause of the smoking etc. Any comments/suggestions appreciated.

Hello Mike. I had my ignition heat up. Noted that it was warm after a drive. Some days it felt hot, so I changed it. Hopefully your wire patch fixed the problem, as those switches as far as I know are not reproduced. Other year Caddy switches will fit but you may have to change your terminal wire hardware to fit. Smaller blades or even ring fittings for example. Another PIA job. If your needle nose pliers removal was not the best, try using a small slot screwdriver which just fits into one of the square notches in the bezel ring. Use a light weight hammer to gently tap the bezel tight. Works very well and is probably better suited for removal due to the "shock" put to the bezel to loosen it. Just got to be careful not to scratch the bezel. So you got to keep the screwdriver in there pressed tight so it won't jump out when struck. Clay/Lexi

[35-709]

Surprised it didn't blow a fuse.  Don't think they used fusible links back then.  Have to wonder why, if just that power wire shorted, did the starter keep on cranking which was alluded to in the first post.  Maybe it wasn't the starter?   

[56Fleetwood]

From what I could see (while folding myself into a pretzel to look under the dash), there are a lot of other wires and cables in that area so rubbing of the IGN wire is a good possibility. 

I just applied 3 coats of liquid insulation and will test the ignition again as soon as I can and will give an update.