My Zoeller M-53 (1/3 HP) sump pump does not switch off. I.e., the sump
pump kicks on fine when the float gets to the level that causes the
pump to kick on. It begins to pump water out like normal but then when
it gets to a certain point, it stops pumping water out. The pump keeps
running but the water level doesn't recede any further. I have to push
the float down a little bit in order for it to stop running.

Any ideas what I could do to fix this problem? Is the switch going
bad?

Thanks,
Kevin