Radon mitigation systems use fans. It could be a very quiet one, or has failed and should be replaced.

As Kudzu points out it's a fan. Typically looks like a wider spot in the tube. More modern installations usually have a pressure gauge (little water manometer) prominently placed to let you know it is operating.

I thought this reminded me of something...

http://ths.gardenweb.com/discussions/3277811/radon-mitigation-detector?n=2

Yes, the radon fan requires electricity. Unless you have one that runs on hamster power and some very active hamsters.

You really should move the fan to the attic, and install a manometer in a visible area before the fan so you know it is working. This is normally a PVC pipe, and not all that difficult to manipulate. If you know how to move electrical, it isnt all that hard to put an outlet box up there for the fan either, otherwise you could call someone to come do it.

It will be worth knowing how to deal with the radon fan anyhow, as they can fail like any motor driven device and usually all it requires loosening a couple fernco boots and hooking up the new fan.

Really appreciate the response. In looking at diagrams of a radon mitigation system online in addition to explanations of the system it always seemed that the fan was in the attic or garage. That is why I asked why I would have electrical wiring running down to my crawl space. Although I haven't looked to see where the fan is on my system it was previously running non stop. Lately it hasn't been doing that and being ignorant of these systems I wasn't sure what the norm was. I'm capable of doing the work that is involved in moving the fan up to the attic, along with the electrical wiring. Again, thanks!

It should run non-stop.

Are you sure you're looking at the wiring for the radon mitigation system and not possibly a sump pump. They both run into holes in the slab typically. One pumps air, the other water. The sump pumps usually have to be wet to operate (won't pump air) so they're down in a pit in the slab.

If it should run non-stop then the fan needs to be replaced. Thanks for that bit of information. Sump pump is on the opposite end of basement. I guess I'll have to cut a section of floor out to get at it. Thanks!