That strange sound at 2 AM

So I awoke about 2 AM, not knowing why....

I laid in bed for a while, trying to figure out what had awoken me....

Then I heard it. That sound that I could not identify.....

Now, if you are a guy, you likely know each and every sound that your house makes (and why), each sound of every piece of machinery, the creaks and groans, the noise every mechanism makes, the sound every pipe makes as it expands and contracts, the groans that the structure makes as it cools or heats up, etc.

This one was none of those. It didn't fit. Wasn't "normal".

So I laid there for a moment, trying to figure out what it was.....
'Twas a low hum.
then it quit.

then it came back.

Then it quit again.
Pretty much about on a 4 minute interval.
Then it came back. More or less 60 hz. Kinda like what a battery charger makes at high amps.....

Strange.

I got up, walked the house....couldn't identify it. Couldn't even localize it.
Put on a pair of shoes and went into the garage. Nothing.
Went down to the basement.
It got a bit louder.

I tracked it down to the east wall. There are only two pieces of equipment there, plus the washer and dryer, both of which are not turned on....but I unplugged them just to be sure that they weren't the source. (They weren't).

Wasn't the water softener, either.

What WAS making that sound was the sump pump.
Seems that the motor (or impeller) was locked up. The motor was TRYING to start, but couldn't turn. So it sat there, stalled, for about 2 minutes, humming gently. Then the thermal cut out would shut off the power and it would cool down.
Wash, rinse. repeat.
(The usual failure mode for these pumps is the bottom bushing wears and they become too noisy for me to tolerate, necessitating replacement)

The sump pit was full, at about 150% of the normal level.

Luckily, (or perhaps it is just good planning, I dunno) I had a spare all set up and ready.
Unplugged the power, pulled the pit cover, unscrewed the union connection to the standpipe, pulled the pump out, put the new pump in the pit, connected the union, plugged it in.
Let it run while I put the pit cover back on.
Total time to change it out was less than 10 minutes, and that long only because I was still only half awake.

I firmly believe that if you need a sump pump, you need a spare on the shelf. "2 is one and one is none" and all that....
Today I gotta go buy a new sump pump.


ETA: And, of course NO-One has the pump I need in stock.
(I still have 2 serviceable, but worn and noisy units as a backup though),