Wouldn't take long for it to rub through a rubber cap.
Sounds like the new switch is bad. Sounds like when your lever makes contact with the plunger that it is grounding the plunger.
Go look at a new switch and have your old one there to compare it to the new one.
The plunger should be insulated on the inside to keep it from grounding to the lever. Sounds like it is missing some parts inside.
