How can I locate a wall from a crawl space?
Cut an opening in the wall for a low voltage box/bracket,and install the bracket.





Position a flexible drill bit into the hole, so that you'll drill straight through the bottom plate of the wall and into the crawlspace.



This is a poor image since the guy is not drilling straight down, but you get the idea.


Go into the crawlspace and attach the cable to the drill bit.
Pull the drill bit (and cable) up into the wall.
Make up the connections to a wall plate, and install the wall plate in the low voltage box/bracket.