I have a sprinkler zone valve stuck open, but IDK where the valve box is.
I have two valve boxes, one has 5 zone valves, the other has the main
valve and two zones. Of course the stuck valve is in the box that I
can't remember where it's located. I've tried cycling the valves, listening
for clicks. I can hear clicks in the box I know, but so far despite listening
where I think the other one could be, no luck. No luck with a pitch fork
in the likely spots either. I do have a map I drew when it was put in
25 years ago, but so far I can't find that either.

So any ideas for a cheap way to put a signal on the wires going to it
and tracing it to find it? The wires are probably 8 inches or so deep.
Maybe a rental company? HD? I looked online at Harbor Freight,
they have an AC one, but it relies on AC power. Any chance of
putting something simple and easy on it and trying an AM radio?