The ignition switch on my 72 240z has the following problem: when I turn the key from lock to accessories and start, it get stuck and I have to play with it several times to finally be able to go to start.

It is not the electrical part of the switch being the problem but the mechanical part where the key goes in.

This part is sealed and i don't see how it can be dismantled to look what is wrong inside.

Is it fixeable or does it need to be replaced?

It can be disassembled, I have done so on my original, as well as on a spare from one of my parts cars. I suspect your tumbler pins (aka wafers) are worn and are jamming. Mine were. I had access to a supply of replacement wafers at that time, so I replaced them all in my original, and re-keyed my spare to match the car as well.

However, knowing what is inside there, I see no reason for you to disassemble it if you don't have access to the replacement wafers. Lacking that, I'd remove the ignition lock from the car and take it to an old-time locksmith.

Edited June 17, 201113 yr by Arne

What Arne said. Took mine to a local lock smith, 2 hours and $25.00 and it was all better with 2 new keys.