Terry S. wrote:
I bought my small one-story house in 1996. It is now about 26 years
old. There is no basement, but there is a crawl space under the
entire house that I store a lot of stuff in. The pipes for the house's
plumbing and the electrical and cable wires are all visible in the
crawl space.

Recently I started hearing loud clicks coming from under the floor in
the living room. I assumed they were coming from the crawl space, but
when I went in it I heard nothing. Now the clicks have turned into
what sounds like a noisy motor..

My oil furnace is in my garage and there's no sound coming from it.
I've gone back into the crawl space and checked it out from wall to
wall and still heard nothing, but when I go back into the living room
the sound is still there.

Any ideas as to what's going on?

Now you know why it's called a crawl space. Get a good flashlight and
happy hunting. If you see glowing eyes looking at you while under there
it's probably not a good thing.