I have a 73 240z and both the hazard knob and switch seem to be fine, but the knob won't stay on.  I know how to line it up and give it 1/4 turn to lock it in, but it doesn't stay.  Maybe I need a longer spring?

Interesting. Chances are something is worn.

If you need a knob or switch let me know.

It sure would be good to know if something is indeed worn or just missing....

The switch operates fine and the knob looks to be in good shape as well.

I have a 73 and it seems to me that your shaft doesn't protrude far enough  to allow the knob to engage. 

Can't believe I just wrote that!! 

Here's some  photos to compare.

 

 

Edited April 13, 201610 yr by Zup
added photos

Thanks for the pictures Zup, and I see what the problem is.  There is a washer of sorts on the shaft that the spring on the knob pushes against, and mine is missing.  I need to find mine, get one from someone else, or fabricate something.  Thanks for the help!

Doubt if this will be helpful, since I don't know exactly what I did, but last year I removed the hazard switch on my '73 to clean the contacts. Somehow, when I reinstalled it in the dash, it ended up with the threaded part of the shaft sticking out through the dash about 1/2 inch too far. I put the retainer and knob back on and left it like that, because it worked and I didn't feel like crawling back under there. And still don't.