Brake switch replacement

diagram for 1997 mercury grand marquis needed. Switch is rotating on mounting pin. Have a spare plastic ring after replacement. don’t know where it goes.

I have never replaced one of these, but it is pretty commonly done. I see two rings in my '99 diagram. One is between the switch and the whatever surface the pin that it mounts is attached to. The other is between the brake master cylinder push rod (and the bushing that goes into it) and the locking pin. Corollary to that is there is nothing between the switch and the rod. Unfortunately, I don’t understand why it would rotate.

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Thanks for the reply and the web site.