1970s Ignition Switch / Steering Column Issues

[BigAnt13]

Having issues with the ignition switch / tumbler on my 1979 Coupe.  Key worked fine, but now does not work and the tumbler does not turn.  Tried to jiggle the steering wheel and column.  Any suggestions?  Thanks!

[The Tassie Devil(le)]

Sounds like you either have a badly worn key, a badly worn lock, or a combination of both.   How well does the key fit in the doors?

Or, if the car has tele/tilt, it could be a broken rack within the steering column itself.

If it is within the column, then these plastic gears can lose teeth, and cause the key/tumbler to not rotate as it operates the steering column lock as well.

I cannot load pictures at this point in time to show you what I am referring to.

Bruce.

[The Tassie Devil(le)]

Here are the pictures I couldn't previously load.

Notice the broken tooth?   This created the problem requiring the replacement part.

Bruce.

[V63]

It was very common for the lock cylinder to simply seize up abruptly.

I had it happen at least twice to me with different different cars. reasonably low miles. Lubricants had no effect.

Replacing the lock cylinder and keys solved the problem.

The steering wheel must be removed.

✅ You will need a tilt wheel column installation kit for reassembly! ✅

There is a tiny retaining screw that will release the prior lock tumbler, slide in new one.

[Chopper1942]

If the cylinder will not turn at all, most likely the metal clip that holds the tumblers and springs in place has come loose. When this happens, the only fix is to take out the cylinder housing and some times you can drill the housing to release the cylinder. But most likely you will need to replace the housing and lock cylinder.

[TJ Hopland]

Hard to tell what the issue is.   Next step has to be get it apart for a look.   Horn pad comes off with screws from behind.  Steering wheel may require a steering wheel puller.  A lock ring tool is just about a requirement for getting good access.   Both of those tools can be had pretty cheap these days.   Sometimes there is an access hole in the lock ring to allow access to the screw that retains the lock assembly but in this case I suspect you will want full access to fully inspect things.

As others mention there can just be wear in the lock.  As in Bruce's photos the gear can have issues as can the 'rack' that the gear engages.  That rack has a curved slot at the end that engages a rod that goes down the column that actuates the electrical switch.  Any of those parts could be jamming up the whole works and the only way to know where the problem is is to start separating things and see when it starts moving or what is still stuck.