For many years going back as far as the late 19060’s Ford has used the same design for their ignition switches. All be it with minor differences in the quality of materials used for casting the main housing of the switch.
The housing on the left is the billet aluminium housing milled by engineers in Melbourne and the one on the right is the factory cast housing used by Ford. Over the years Ford has used a part that slightly differed in the casting material used which can physically be noticed when squeezing the metal and working with it.
Unfortunately the cast material deteriorates like sand stone over the years in which the spring that returns the key after starting chips away at the metal pieces its attached to. The spring pictured inside the white plastic part will either break off the metal tab or twist the whole part putting pressure on the wiring loom attached to it forcing it to fall apart. Again the cast metal material isn’t strong enough to hold the switch together whilst the internals are twisting.
The failure rate is very unpredictable as to when the ignition switch will fail, we’ve worked on vehicles with 60,000km and others with 580,000km. There seems to be no correlation between the condition of the ignition switch and the functionality of the key and barrel mechanism since the ignition switch is a spring loaded system floating on ball bearings. It ultimately depends on how the spring chips away and twists inside the switch year after year.
Summer time however seems to be the biggest trigger for failure with a large percentage falling apart mostly due to the grease melting inside the switch and lubricating the edges allowing for the wiring loom to wriggle loose. There will often be no indication something is wrong when you jump in the car, we have many customers arrive at the shops etc. come back to their car and its fallen apart without warning.
If you are fortunate enough that the spring stops working and doesn’t return to the accessories position after starting then do yourself a favor and get it fixed. It could be anywhere from days to years away before it falls apart.