Lock Cylinder Not Engaging Ignition Switch Rod

[Mark E.]

This failure happened in stages. First, the Start position did not work but Accessory, Lock and On were operable. I checked that the switch was snug to the column and connected to the rod that connects it to the lock cylinder. After turning the key a few times during this check, all of the switch positions (Acc, On, Start) stopped working, the rod stopped moving and the lock cylinder does not feel engaged as the key rotates.

So the rod between the lock cylinder and ignition switch is attached to the ignition switch but does not move when the lock cylinder is turned. It seems like the upper end of the rod isn't connected to the lock cylinder. CSM instructions for R&R of the lock cylinder does not mention the rod which suggests there's something else that connects the lock cylinder to the rod.

What failed and how is this fixed?

[John S.]

Re: Lock Cylinder Not Engaging Ignition Switch Rod

Mark, if your car is equipped with tilt/tele, the lock cylinder is connected to the rod going down to the ignition switch by a plastic gear and a metal rack/cam see the attached photos.

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[Mark E.]

Re: Lock Cylinder Not Engaging Ignition Switch Rod

Thanks John!

Yes it's a tilt and Tele.

Can this repair be done with the column in the car? I just restored the interior and desperately don't want to remove the column.

[John S.]

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Good luck and let me know if you have any questions.

[Mark E.]

Re: Lock Cylinder Not Engaging Ignition Switch Rod

Thanks again John.

I was leaning to farming this out, but your posts have me thinking about tearing it down to at least to check the plastic gear. From your posts, R&R of the gear looks straight forward working from the top of the column.

[John S.]

Re: Lock Cylinder Not Engaging Ignition Switch Rod

Mark, yes most of the work getting to the gear will be from the top end but you will have to go underneath to disconnect the harmonica connector that goes up the the directional signal switch. That connection needs to be undone to get enough slack in the wire to remove the upper housing cover to expose the gear as shown in my earlier photos.

No need to remove the wiring all the way out unless you’re going to replace the direction switch, see the attached photo. I also recommend removing the small spring clip on the bottom of the column that holds the lower trim panel in. Removing it gives you more clearance to slide the wires, they like to get snagged on that clip, photo also attached.

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If your going to attempt this, photograph everything as you take it apart and keep the parts in order as you take them off. There are also some good videos on Youtube. Watch a few before you dive in.

[Mark E.]

Re: Lock Cylinder Not Engaging Ignition Switch Rod

Well, I've decided to not repair this myself for a couple of reasons. First, after looking at the overhaul manual and several videos, it seems near impossible for a guy who hasn't done it before to disassemble and reassemble the column without screwing up installation of the scores of fiddly parts inside or breaking something. It's just one of those jobs that take a few times to learn how to do, especially without help. Second, it turns out that one of the few guys who knows these columns lives about 90 minutes away- Larry Smith of CorvetteColumn.com . And since it's 54 years old, it probably needs a thorough rebuild anyway.

So my remaining challenge is R&R of the column. I've done that several times on non-Corvette GM cars and I read the CSM but I have a dumb question:

How are the two nuts that hold the column to the bulkhead accessed? They are covered by a plastic trim piece and it's not obvious how it's removed; see photo. No fasteners seen; is it attached with the carpet plugs? No mention of this piece in the CSM.

Thanks again folks.


70 Corvette Steer Column Bulkhead Connection 2.jpg

[John S.]

Re: Lock Cylinder Not Engaging Ignition Switch Rod

Mark, probably a smart move to have it rebuilt by someone with some experience. Not a good first time project by yourself. As you stated, lots of parts and pieces.

Regarding your plastic cover, here’s what I found in the ‘70 AIM. See items 3, 4 and 5. Looks like the plastic shield and the insulation behind it is held in by rubber plugs, one on each side. It also looks like both pieces have U shaped reliefs to clear the two carpet plugs shown in your pics. Not sure if you have to remove the two going through the carpet but you’re going to have to find and remove the two on the sides. See attached photo.

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Now having found and said all that I started to wonder about my ‘73 which has no such cover. I found a page in the ‘72 AIM that is almost identical to the page above, however apparently there was a change starting in ‘73 that included a different insulation mat that eliminated those two components and the associated plugs. I still have the two carpet plugs but nothing else, the two bolts for the column are totally exposed. Learn something every day.

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Hope this helps and good luck on your column, let us know what the rebuilder finds.

[Mark E.]

Re: Lock Cylinder Not Engaging Ignition Switch Rod

Thanks again John. I didn't see any fasteners for the cover, only the carpet plugs- I'll take another look under there. Besides figuring out how to remove this cover, the remaining job of removing the column should be straight forward.

I once owned a 1973 L82 M20 AC coupe...loved it. As you say, I believe it didn't have this cover. GM cars from the mid-60s on are a study in decontenting and cost cutting. This cover may be an example. Another example in the footwell is deleting bright trim on the pedals in 71 or 72.

[Mark E.]

Update on the steering column-

Pulling the steering column was straight forward. A couple of notes:
- Removing the steering wheel first makes the job easier
- The plastic trim piece I asked about above at the base of the column on the inside of the cowl is attached with the carpet plugs. Pull those out and the trip piece can be wiggled out. This reveals the two studs and nuts fastening the column to the cowl.
- Removing the metal bracket for the transmission lock cable reveals a slotted hole in the cowl. The column can then be easily pulled through that hole.

I took the column to Larry Smith of corvettecolumns.com in Canton, TX. He's worked on these for decades and is one of the few go-to guys left in the country. And bonus: he's just a two hour drive away. I appreciated his attention to details and doing it right. He has an inventory of rare NOS column parts too that he uses. He replaced a lot of wear parts proactively with NOS (turn signal switch, sector gear and rack, key warning switch, bearings, ignition switch, upper and lower bearings to name a few). Turn-around was 10 days. After seeing the disassembled column, I'm glad I took it to Larry. Like overhauling an automatic transmission, it's one of those jobs that's hard to do properly on your own for the first time.

Cause of failure? A tooth on the plastic sector gear broke off which disengaged the lock cylinder from the rod going to the ignition switch. Why? 55 year old plastic gear, or perhaps too much force required to move the ignition switch and rod.

The column looks great and now awaits installation.

[John S.]

Mark, glad to hear to got the column out and sounds like you’ve got a great rebuild. I would say the broken gear is either 55 yr old plastic as you state or something may have been binding.

Before you put the column back in, you may want to check the function of the interlock cable from the transmission. You should have disconnected that cable on the engine side of the firewall for the column removal.

While the interlock cable is not directly connected to the ignition switch or to the gear/rack assembly it does interact with it when the car is put into park to activate the column lock. I’m not sure how the cable routes on automatics but I’d check it to make sure it operates smoothly by hand. They do have a tendency to bind with age and normal wear.

Good luck on the installation.

[Mark E.]

Mark, glad to hear to got the column out and sounds like you’ve got a great rebuild. I would say the broken gear is either 55 yr old plastic as you state or something may have been binding.

Before you put the column back in, you may want to check the function of the interlock cable from the transmission. You should have disconnected that cable on the engine side of the firewall for the column removal.

While the interlock cable is not directly connected to the ignition switch or to the gear/rack assembly it does interact with it when the car is put into park to activate the column lock. I’m not sure how the cable routes on automatics but I’d check it to make sure it operates smoothly by hand. They do have a tendency to bind with age and normal wear.

Good luck on the installation.

John,

Thanks for your help through this project.

Yes, it's important the interlock cable operate smoothly. I've replaced the cable twice over 35 years of ownership.

PSA: Be gentle when shifting into reverse in '69 and up C3s with 4-speed. The interlock cable can easily bend while PUSHING a lever on the column. Once bent, it doesn't work well. Using a cable to apply compression force is a poor and fragile design.