QUOTE(aircooledtechguy @ Feb 4 2012, 02:19 PM)
I've run into similar problems on late model air-cooled VW beetles (which have a similar ignition switch/key/steering lock arrangement).
What I have found is that sometimes it's the piece that is between the key tumbler and the electrical switch. This little section that actually works the steering lock is basically 2 flat discs that have an off-set cam that works the steering lock. I've found that over time, they can actually twist slightly (probably brought on my someone forcing the key with pressure on the steering lock) and it now prohibits the electrical switch from turning enough to engage the correct tabs internally. The only solution I've found for cars with this problem, is to replace the entire steering/lock assembly since you can't get just the part that is worn.
When this has been the issue, the ignition key will only engage the "ON" position, not the "start" (though you can feel the spring tension that the start position has; it just won't engage the starter motor and there's no indication of load on the dash lights). If you remove just the electrical portion of the switch the engine fires right up using a screw driver = the switch is not being turned far enough = bad steering/lock assembly. I go and install a good used steering/lock assembly, and the cars start right up using the same key tumbler and electrical switch. . .
This may not be the problem you are experiencing, but it's one that I have run into here at my shop several times over the past couple years. . .
Ding ding! Give that man a cigar!
I don't know what the "discs" are but the cam that interlocks with and rotates the switch was worn and twisted backwards. effectively reducing the amount of rotation that can be achieved with a full turn of the key.
Click to view attachment The area in the oval is the contact/pushing surface of the shaft and it did look worn and a bit pushed backward.
I was able to compensate for this by trimming the backside of the locating tabs(one for the set screw and the other is just a little peg) allowing the switch to be clocked backwards. Effectively adding back the lost rotation due to wear/twist. I shimmed the other side to take up the slack. Sure it 's a bit of a hack job on the replacement switch but it works now.
I guess you could build up the area that was worn/pushed back to regain full rotation but I couldn't figure what would hold well to the metal and I don't weld yet, if that would even be appropriate.
Another option would be to twist the "cam" back to it's proper place but I was worried I would snap it off instead of bending it.
Thanks for your help.