Most used or old ignition switches (the electrical body) have sufficient wear and/or internal crap to make them a flakey proposition (open circuits or intermmittents) but if you can't get an aftermarket switch quickly & cheaply they can be quickly refurbished at no cost and no stress to give as new reliability. Carefuly with a 2mm blade screwdriver bend back the 4 alloy retainers holding the metal body to the plastic body to separate these and lift out the cam - the internals are all fixed - some switches have a removable detent pin and spring though - its not like spilling a bag of marbles. Use fingers to separate contacts to put fine grit aluminium oxide paper between contacts, then close contacts and pull paper out - and muck with it. Turn paper around to do other contact of each pair. If little resistance to pull then bend spring-copper contacts with long nose pliers to increase mating force. Little resistance is due to poor quality control at factory - most of these contacts mate with aggressive force. Wash all in degreaser to get rid of muck around outside of contacts and hold contacts open when washing. After blow dry check all contacts to ensure no brush hairs stuck in them. Put some fresh grease in the "detent" holes at the bottom of the metal body. Bend contact fingers out slightly to reseat the cam and rotate it so that its detent ball aligns with the "track" in the metal body. THe metal and plastic switch bodies have an alignment slot. Holding the switch together by hand or tape then stick a screwdriver in the top of the switch to check that it moves freely between positions 0, I, II and force is need to get position III, which on release snaps back to II, and that the amount of turn angle between positions is similar to the turn of your ignition key. Check it out with an ohmmeter as per the switch table in wiring diagrams in Haynes or Bentley if you want more confidence. Only then use a hammer & drift to bend the 4 alloy retainers back. Voila - your reliable "brand new" switch in less than one hour.

sutherml in Adelaide, Australia
1979 244 GL @ 518,000 km
converted to gas (LPG) in 1991