Is your question due to a problem or curiosity? Just in case, I'll assume you want it to pump water but it won't.

The first plug is for the float switch. It will activate the pump when the sump fills to the set level to energize the pump. If your sump is full of water and the switch doesn't activate the pump, it is either not functioning or, it needs to be adjusted.

Don't reach down into the sump and lift up on the switch (if it's the submersible type). Take a stick and lift up on the float. If it activates the pump, then it would just need adjustment. Otherwise, you will need to replace the float switch. Sometimes you can shake it and it will resume working. However, it might stick again when you need it most. They're cheap enough to replace for reliability sake.

I agree a new switch is recommended if there is any chance of a problem with the existing. Once you remove the pump from the pit, the switch should be attached to the top of the pump and should be relatively easy to remove.

If your basement is finished you may want to look at a NexPump Ai System. It is an awsome failsafe primary and backup sump pump system.

Here is a link that might be useful: The Inteligent Sump Pump

Excuse my ignorance, but it sounds like a bad piggyback plug. I have the same problem.

What's the current best sump pump price.