If the contacts inside the switch are bad, then the relays that the switch powers up will have their power interupted, thus causing the relays to open and close, unexpectedly, creating a clicking.
The screws in question are breakaway screws, and are designed to have their heads break off at just the right torque for being tightened. Makes it harder to steal, supposedly. You're going to need an easy-out extractor, or a drill and a steady hand.
Take care,
~Chris
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