74 duster brake light switch

This is another of those things I picked up while playing hookie from school and hanging around a garage back in the early 70s. A customer would come in and say, " I got in a panic stop situation yesterday and hit the brakes HARD ! Now this brake light wont go off ".
The mechanic would look everything over, do something at the proportion valve to correct the fault ( make the lamp go off ) and tell his customer, " If it comes on again in a day or 3 of normal operation, bring it back. We'll likely need to replace the master cylinder ".
It'll be much easier to ignore me and leave it unplugged.